(200 + 20 ⋅ x) - 200 = 160
200 + 20 ⋅ x = 160 + 200
200 + 20 ⋅ x = 360
20 ⋅ x = 360 - 200
20 ⋅ x = 160
x = 160 : 20
x = 8
Ответ: 8