Решить уравнения: 1) 9*b+6*b - 15 = 615 2) 2*a+123*a+97 = 472 3) 1728: (56 - x) = 36

1)  9*b+6*b - 15 = 615
15b = 615 +15
15b = 630 /:15
b = 42
2)  2*a+123*a+97 = 472 
125a = 472 - 97
125a = 375 /:125
а = 3
3)  1728:(56 - x) = 36
1728 = 36 * (56 - х)
1728 = 2016 - 36х
36х = 2016 - 1728
36х = 288 /:36
х = 8