Simple: 1 / 6 × 2 / 5 (5 / 6-3 / 4) 39 / 5 × 55 / 26 / 11 / 3 (11.4-4.2) × 5 / 9 Do a good job and add points

Simple: 1 / 6 × 2 / 5 (5 / 6-3 / 4) 39 / 5 × 55 / 26 / 11 / 3 (11.4-4.2) × 5 / 9 Do a good job and add points

1/6×2/5÷(5/6-3/4)
=1/15÷(10/12-9/12)
=1/15×12
=4/5
5/39×26/55÷(3/11)
=1/39×26/11×11/3
=2/3/3
=2/9
(11.4-4.2)×5/9
=7.2×5/9
=0.8×5
=4

13 × (5 / 26 + 5 / 39) 2 ／ 4 / 3-4 / 3 4 / 2 15 / 8 × 12 / 7 16 (how simple and how to calculate)

13 × (5 / 26 + 5 / 39)
=13x5/26+13x5/39
=5/2+5/3
=25/6
4 / 2-4 / 3
=2x3/4-3/4x1/2
=3/4x(2-1/2)
=3/4x3/2
=9/8
8 out of 15 × 12 ÷ 16 out of 7
=8/15x12x7/16
=8/15x3x7/16x4
=8/5x7/4
=14/5

A math problem: there are 40 pieces of RMB 10 yuan and 5 yuan, a total of 325 yuan. How many of these two kinds of RMB?
There are 40 pieces of RMB 10 yuan and 5 yuan, a total of 325 yuan. How many of these two kinds of RMB? No equation

If there are x sheets of 10 yuan, there are (40-x) sheets of 5 yuan
Equation: 10x + 5 (40-x) = 325
The solution is x = 25
40-X=15
A: there are 25 tickets for 10 yuan and 15 tickets for 5 yuan
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Let n denote any integer, and the algebraic expression containing n denotes the product of three consecutive integers

N (square of n-1)

Simple operation: 18 × 5022-18 × 4982

18×5022-18×4982=18（5022-4982）=18（502+498）×（502-498）=500．

The base of a triangle is 5.6CM long. After extending the base by 2cm, the area of the triangle will be increased by 5cm

2S/5.6=5,
∴S=5*5.6/2=14,
Answer: triangle area is 14 square centimeter

Divide X by 80% + 9 / 10 = 3 and solve the equation,

x÷80%+9/10=3
(5/4)x=3-9/10
x=21/10 × 5/4
x=42/25

A triangle plywood, the area is 56 square decimeters, one of his sides is 16 decimeters long, how many decimeters is the height of this side?

56 × 2 △ 16 = 7 decimeters

400 △ 25 + 99 × 2 = simple calculation

=4×(100÷25)+(100-1)×2
=16+198
=214

It is known that: as shown in the figure, in △ ABC, D is the midpoint of AC, e is a point on the extension line of line BC, the parallel line passing through point a as be intersects with the extension line of line ed at point F, connecting AE and cf. (1) verification: AF = CE; (2) if AC = EF, try to judge what kind of quadrilateral afce is, and prove your conclusion

(1) It is proved that: in △ ADF and △ CDE, ∵ AF ≌ be, ∵ fad = ∠ ECD. And ∵ D is the midpoint of AC, ∵ ad = CD. ∵ ADF = ∠ CDE, ≌ ADF ≌ CDE. ≌ AF = CE. (2) if AC = EF, then quadrilateral afce is a rectangle. It is proved that: (1) AF = CE, AF ∥ CE, and ≌ quadrilateral afce are parallelograms