У меня возник вопрос. Помогите пожалуйста. закончи вычисления  39×12=39×(10+2)= 72×20=72×(2×10)= 40×35=40×(30+5)= 40×35=35×(4×10)= 152×30=152×(3×10)=

39 * 12 = 39 * (10 + 2) = 39 * 10 + 39 * 2 = 390 + 2 * (30 + 9) = 390 + 60 + 18 = 468;

72 * 20 = 72 * (10 * 2) = = 72 * 10 * 2 = 720 * 2 = 1440;

40 * 35 = 40 * (30 + 5) = 40 * 30 + 40 * 5 = 1200 + 200 = 1400;

40 * 35 = 35 * (4 * 10) = 35 * 4 * 10 = (30 + 5) * 4 * 10 = (30 * 4 + 5 * 4) * 10 = (120 + 20) *

* 10 = 140 * 10 = 1400;

152 * 30 = 152 * (3 * 10) =152 * 3 * 10 = (150 + 2) * 3 * 10 = (150 * 3 + 2 * 3) * 10 = (450 +

+ 6) * 10 = 456 * 10 + 4560.