2.7b+3.4c+3.5b-8c b=2.C=3

если b=2, c=3, то 2.7b+3.4с+3.5b-8с=2.7*2+3.4*3+3.5*2-8*3=-1,4

2.7b+3.4c+3.5b-8c=2.7b+3.5b+3.4c-8c=6.2b-4.6c=6.2×2-4.6×3=12.4-13.8=-1.4