x + 7 = 19
x = 19 - 7
x = 12
x - 8 = 15
x = 15 + 8
x = 23
4x = 28
x = 28 / 4
x = 7
x : 6 = 5
x = 5 * 6
x = 30
Ответ: 1) x = 12; 2) x = 23; 3) x = 7; 4) x = 30