The area of a trapezoid is 56 square centimeters, its upper bottom is 13 centimeters, and its lower bottom is 15 centimeters Please! Do it for me! Do it for me!

Height h = 4cm
Formula: trapezoid area s = (upper bottom a + lower bottom b) × height h △ 2, so height h = 2S / (a + b) = 2 * 56 / (13 + 15) = 4cm

The area of a trapezoid is 56 square centimeters, the upper bottom is 6 square centimeters, the height is 7 square centimeters, and the lower bottom is () square centimeters?
The area of a trapezoid is 56 square centimeters, the upper bottom is 6 square centimeters, the height is 7 square centimeters, and the lower bottom is () square centimeters

We know that the area formula of trapezoid is (upper bottom + lower bottom) × height △ 2, so lower bottom = area × 2 △ height upper bottom = 56 × 2 △ 7-6 = 10

How many math problems do not know how to do?
1: When we transport a batch of coal, three tenths of this batch of coal will be transported in the first time, and four tons will be transported in the second time. There are still 31 tons left. How many tons of this batch of coal are there?
2: For a book, the ratio of the number of pages Xiao Ming read on the first day to the total number of pages is 1: if he read another 50 pages, he can read half of the book. How many pages is the book?
3: The ratio of the number of pages Xiao Ming reads to the number of pages left in a book is 1: if he reads another 50 pages, he can read half of the book. How many pages are there in the book?
4: In an alloy of copper and tin, the weight ratio of copper to tin is 7: it is known that copper is 900 grams more than tin. How many kilograms of this alloy?
5: How much less is 4kg than 5kg? How much more is 5kg than 4kg?
Help me spread it

1: There are 50 tons of coal in this batch
2: The book has 200 pages
3: The book has 167 pages
4: This alloy weighs 5.4 kg
5: 4 kg is one fourth less than 5 kg
5 kg is one fifth more than 4 kg

There are five Mondays and four Tuesdays in June of a certain year. What day is the first day of June of this year?

The 30th is Monday, four weeks ahead is the 2nd, it's Monday, so the 1st is Sunday

Mathematics frequency and its distribution in grade two
Class 9.2 of a school investigated all the students of grade 9 who reached the sports standard (above 60 points, including 60 points). They investigated the sports standard of 50 students in their class and other classes
Class 9.2: score, 40-60, 60-80.80-100, frequency, 0.02, 0.66, 0.32
Grade nine: 40-60:12.5%, 60-80,55%, 80-100,32.5%. If the sports standard rate of the whole class is not less than 90%, the number of students in the whole class is not more than 90%

All x, then: except 9.2 class number: x-50
（x-50）*（0.55+0.325）+50*(0.66+0.32)>=0.9x
And then it can be solved

In the multiplication of natural numbers, there are some interesting mirror symmetries, such as 12 * 231 = 132 * 21. If 18 * 8X1 = 1x8 * 81, try to find the value of X

Is it so simple to ask?
Just unfold 8X1 and 1x8
8x1=800+10x+1,1x8=100+10x+8
It can be replaced by the original formula

If x square-7x-15 = (x + m) (x + n), then M + n =?
It is said to be cross multiplication. Please explain the solution
The equation for X is (m square + 2m-3) times the | m | - 1 power of X + 5x = 12
(1) Can he be a linear equation with one variable? If so, what is the value of M and find his solution
(2) Can it be a quadratic equation of one variable? If it is, what is the value of M
Personal calculation is totally inconsistent with the answer, and I don't know what's wrong
3 if the 2A + B power of x-3 (a-b power of x) + 1 = 0 is the value of a and B obtained by the quadratic equation of one variable about X
Three questions have answers in hand, mixed points do not come

The first problem is that we can get x square + (M + n) x + Mn = x square - 7x-15, because the equation holds, so m + n = - 7... The second problem (1): maybe, because the power of 0 of the constant except 0 is 1, so it holds if and only if | m | - 1 = 0, so m = positive or negative 1. Then, when m = 1, the original formula = (1 + 2-3

Use the four numbers 3; - 5; 2; - 13 in one operation to make the result equal to 24
emergency

3-5-2×（-13）=24
3×2-（-13-5）=24

If every two students shake hands at a party of nine students, how many times?

Using mathematical permutation and combination, 9 * 8 / 2 = 36

Simple operation: 6.3 * 27 + 1.9 * 21

6.3*27+1.9*21
=21*0.3*27+1.9*21
=21*(4.1+1.9)
=126
The correct rate is 100%

The area of a trapezoid is 56 square centimeters, its upper bottom is 13 centimeters, and its lower bottom is 15 centimeters Please! Do it for me! Do it for me!