(4 ⋅ a - 16) : 4 = 5
4 ⋅ a - 16 = 5 ⋅ 4
4 ⋅ a - 16 = 20
4 ⋅ a = 20 + 16
4 ⋅ a = 36
a = 36 : 4
a = 9
Ответ: 9