410 - (b ⋅ 8 - 40) = 378
b ⋅ 8 - 40 = 410 - 378
b ⋅ 8 - 40 = 32
b ⋅ 8 = 32 + 40
b ⋅ 8 = 72
b = 72 : 8
b = 9
Ответ: 9