Решим выражения по порядку действий:
(120 - 20) : 5 ⋅ 4 = 100 : 5 ⋅ 4 = 20 ⋅ 4 = 80
120 - 20 : (5 ⋅ 4) = 120 - 20 : 20 = 120 - 1 = 119
120 - 20 : 5 ⋅ 4 = 120 - 4 ⋅ 4 = 120 - 16 = 104