2) 1 способ : Sabcd = AB * BC
Sabcd = 4 * 12 = 48
2 способ : Sabkm = AB * BK ; Skmcd = MK * KC ; Sabcd = Sabkm + Skmcd
Sabkm = 4 * 8 = 32 ; Skmcd = 4 * 4 = 16 ; Sabcd = 32 + 16 = 48
3) (3 + 6) * 4 = 9 * 4 = 36
(5 + 8) * 5 = 13 * 5 = 65
3 * (7 + 2) = 3 * 9 = 27
1+13/22 = 1 целая и 13/22
21*(21/7*3)*(21/7*3/3*10)=21*9*30=5670 см кубических