1)25 + ( х - 2 ) * 15 = 70
25 + 15х - 30 = 70
15х = 70 - 25 + 30
15х = 75
х = 5
2) 72 / ( 12 - х / 4 ) = 9
72 / ((48 - х) / 4) = 9
72 * ( 4 / 48 - х ) = 9
288 / ( 48 - х ) = 9
48 - х = 288 / 9
48 - х = 32
- х = 32 - 48
- х = - 16
х = 16 можно проще
72 / (12 - х / 4 )= 9
12 - х / 4 = 72 / 9
12 - х / 4 = 8
- х / 4 = 8 - 12
- х / 4 = - 4
х / 4 = 4
х = 4 * 4
х = 16
