1) Закончи вычисления. 54.15=54·(10+5)= 214-20=214·(2·10)= 30·28=30·(20+8)= 30-28=28·(3·10)=

Решение: 54 * 15 = 54 * (10 + 5) = 54 * 10 + 54 * 5 = 540 + 270 = 810 214 * 20 = 214 * (2 * 10) = 214 * 2 * 10 = 428 * 10 = 4280 30 * 28 = 30 * (20 + 8) = 30 * 20 + 30 * 8 = 600 + 240 = 840 30 * 28 = 28 * (3 * 10) = 28 * 3 * 10 = 84 * 10 = 840