1) 2 5/9 - 120/21 = 23/9 - 120/21 = → (общий знаменатель 63) → =
= 161/63 - 360/63 = - 199/63
2) - 199/63 : 1 8/49 = - 199/63 * 49/57 = - 1393/513
3) 1 8/9 : 6 = 17/9 * 1/6 = 17/54
4) - 1393/13 + 17/54 = - 75222/702 + 221/702 = - 75001/702 =
= - 106 целых 589/702
Sп=2*П*5,2*(5,2+7)=10,4*П*12,2=126,88*П
Sб=2*П*5,2*7=72,8*П
У-12у=-6-27
-11у=-33
у=-33 : (-11)
у= -3