How do 10 {0.7x - (x-45)} = 12 {x-26 - (x-45)} solve this equation

How do 10 {0.7x - (x-45)} = 12 {x-26 - (x-45)} solve this equation

10{0.7X-(X-45)}=12{X-26-(X-45)}
10(0.7X-X+45)=12(X-26-X+45)
10(-0.3X+45)=12×19
-3X+450=228
3X=450-228=222
X=222÷3
X=74

Help me to solve some math problems with proportion equation
Xiaofang wants to use the shadow to measure the height of the teaching building. She takes a 2-meter-long bamboo pole and stands vertically on the ground. The shadow of the bamboo pole is 1.2 meters long and the shadow of the teaching building is 2 meters long. Please help Xiaofang calculate the height of the teaching building

Because the height of an object is greater than the length of the shadow, and the ratio is fixed at the same time, the height of the building is equal to the height of the bamboo
Y/2=2/1.2
Y = 2 * 2 / 1.2 = 3.3333 or 10 / 3

2 mathematical problems, solving with equations
1. After 16 hours, ship a landed 70 kilometers behind ship B. ship a traveled 30.5 kilometers per hour. How many kilometers per hour did ship B travel?
2. A pen and a ballpoint pen are 8.3 yuan in total. The price of a pen is 0.8 yuan more than twice that of a ballpoint pen. How much are a pen and a ballpoint pen?

1. Suppose that the boat B travels x kilometers per hour. According to the meaning of the question, (x-30.5) × 16 = 70, the solution is x = 34.875 kilometers. A: the boat B travels 34.875 kilometers per hour. 2. Suppose that the price of a pen is x yuan, then the price of a ballpoint pen is 8.3-x yuan

13X - 12 (x + 2) = 0, the process of solving the equation

13x-12(x+2)=0
13x-12x-12*2=0
x-24=0
x=24

The prime numbers in natural numbers are arranged in a column from small to large: A1, A2 an… Then a1 + A2 + +a10=______ When a1 + A2 + +When an = 281, then n=______ ．

（1）a1，a2，… an… A10 = 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 29 = 129; (2) 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 29 + 31 + 37 + 41 + 43 = 281; when added to 43, the sum is exactly 281, 43 is the 14th item, so n = 14

Solution x-14x + 48 = 0

48=13x
x=48/13

If the average of a set of data x1, X2, X3, X4 and X5 is 2 and the variance is 1 / 3, then
If the average of one group of data x1, X2, X3, X4 and X5 is 2 and the variance is 1 / 3, what are the average and variance of another group of data 2x1 + 3, 2x2 + 3, 2x3 + 3, 2x4 + 3 and 2x5 + 3?

ABCDE is used to replace x1-x5
A + B + C + D + E / 5 = 2, that is, a + B + C + D + e = 10;
(A-2)^2+(B-2)^2+(C-2)^2+(D-2)^2+(E-2)^2
=(A^2-4A+4)+(B^2-4B+4)+(C^2-4C+4)+(D^2-4D+4)+(E^2-4E+4)
=A^2+B^2+C^2+D^2+E^2-4(A+B+C+D+E)+20
Know [a ^ 2 + B ^ 2 + C ^ 2 + D ^ 2 + e ^ 2-4 (a + B + C + D + e) + 20] / 5 = 1 / 3;
We also know that a + B + C + D + e = 10;
Then we can get a ^ 2 + B ^ 2 + C ^ 2 + D ^ 2 + e ^ 2 = 65 / 3;
The rest is simple:
average
[(2a + 3) + (2B + 3) + (2C + 3) + (2D + 3) + (2e + 3)] / 5 (brackets should be omitted)
=[2 (a + B + C + D + e) + 15] / 5 (substitute a + B + C + D + e = 10)
=(2*10+15)/5
=7
variance
[(2A+3-7)^2+(2B+3-7)^2+(2C+3-7^2)+(2D+3-7)^2+(2E+3-7)^2]/5
=[(2A-4)^2+(2B-4)^2+(2C-4)^2+(2D-4)^2+(2E-4)^2]/5
=[(4A^2-16A+16)+(4B^2-16B+16)+(4C^2-16C+16)+(4D^2-16D+16)+(4E^2-16E+16)]/5
=[4 (a ^ 2 + B ^ 2 + C ^ 2 + D ^ 2 + e ^ 2) - 16 (a + B + C + D + e) + 80] / 5 (substitute into two calculated numbers)
=(4×65/3-16*10+80)/5
=4/3

1. We know that x ^ 2 + 2 (M-3) x + 25 is a complete square, M =?
2. Factoring polynomials into factors equal to

X ^ 2 + 2 (M-3) x + 25 is a complete square
4(m-3)^2-100=0
m1=8
m2=-2
Decompose polynomial x ^ 2 + 2 (M-3) x + 25 into factor = (x ± 5) ^ 2

As shown in the figure, De is the median line of △ ABC, M is the midpoint of De, and the extension line of CM intersects AB at point n, then s △ DMN: s quadrilateral anme equals ()
A. 1：5B. 1：4C. 2：5D. 2：7

∵ De is the median line of △ ABC, ∵ de ∥ BC, de = 12bc. If the area of △ ABC is 1, according to de ∥ BC, ∥ ade ∥ ABC, ∥ s ∥ ade = 14, am is connected. According to the title, s ∥ ADM = 12S ∥ ade = 18S ∥ ABC = 18, ∥ de ∥ BC, DM = 14bc, ∥ DN = 14bn, ∥ DN = 13bd = 13ad. ∥ s ∥ DNM = 13s ∥ ADM = 124, ∥ s quadrilateral anme = 14 − 124 = 524, ∥ s ∥ DMN: s quadrilateral anme = 124:524 =1: 5. So a

Minus one ninth to the power of 2012 multiplied by nine to the power of 2013
(- 1 / 9) power of 2012 × power of 9

(- 1 / 9) power of 2012 × power of 9
=(1 / 9) power of 2012 x 9
=(1 / 9x9) 2012 power x9
=1x9
=9