с математикой !
Только 2, 4 и 5 задание

5.

8a + 6b – 6a – 18b= 2a – 12b = -2(6b - a)

6b – a = -1,9; - 2.(-1,9) = 3,8

4.

1) -7a +15 - 1+2,5a - 3, 2a - 12 = 2- 7,7a

a=5/7 2-77×5/10×7=2-11×1/2×1=2-11/2=2-5,5=-3,5

2.

1) 4,2×6xy = 25, 2xy

2) -5m + 4 p.

3) k-17+k-k+30=k+13

4) -24 – 6a + 8a - 48 = 2a – 72.