a) 3,5 ⋅ 6,8 + 3,5 ⋅ 3,2 = 3,5 ⋅ (6,8 + 3,2) = 3,5 ⋅ 10 = 35
б) 12,4 ⋅ 14,3 - 12,4 ⋅ 4,3 = 12,4 ⋅ (14,3 - 4,3) = 12,4 ⋅ 10 = 124
Ответ: a) 35; б) 124