Ответ: а) 3,9у; б) 24,89m
а) 8 ⋅ 3,9y ⋅ 0,125 = 8 ⋅ 0,125 ⋅ 3,9y = (8 ⋅ 0,125) ⋅ 3,9y = 1 ⋅ 3,9y = 3,9y
б) 0,5 ⋅ 2,489m ⋅ 20 = 0,5 ⋅ 20 ⋅ 2,489m = (0,5 ⋅ 20) ⋅ 2,489m = 10 ⋅ 2,489m = 24,89m