Вычисли, выбирая удобный порядок действий: a) 8 ⋅ 197 ⋅ 125; b) 39 ⋅ 71 + 39 ⋅ 29; c) 45 ⋅ 15 − 15²

a) 8 ⋅ 197 ⋅ 125 = 8 ⋅ (125 ⋅ 197) = 8 ⋅ 24625 = 197000. b) 39 ⋅ 71 + 39 ⋅ 29 = 39 ⋅ (71 + 29) = 39 ⋅ 100 = 3900. c) 45 ⋅ 15 − 15² = (45 − 15) ⋅ 15 = 30 ⋅ 15 = 450.