ответ:1)4,2)2,3)0
1) x = 16.25
x != 13
x + 13 = 9(x-13)
x + 13 = 9x - 117
x -9x + 13 = -117
-8x = -117 - 13
2) 13
x != 7
3x - 21 = x + 5
2x = 26
x = 13
3)0
