Ответ:

1) 5а+4а= 225-81

9а = 144

а= 16

2) -7х-9х= 26-10

-16х = 16

х= - 1

3) 24х + 40 = 36х + 12

24х - 36х = 12- 40

-12 х= - 28

х = 7/3

4) 9х+ 1 - 21 = 24х+ 15

9х-24х = 15-1+21

-15х = 35

Х = - 7/3