a(b-4)-b(a-3)=ab-4a-ab+3b=-4a+3b=-4*2,5-3*1/3=-10-1=-11

1)2a-1,5a+7,5a-3a=5a, a=-2,75, 5a=5(-2,75)=-13,75

2)3a-1,5b+7a-8,5b=10a-10b=10(a-b), a=1,7,b=-4,3,

  10(a-b)=10(1,7+4,3)=60

3)-2(x-2y)+(9y+2x)=-2x+4y+9y+2x=13y, y=1,2

13y = 13.1,2=15,6

4)a(b-4)-b(a-3)=ab-4a-ab+3b=-4a+3b

  a=2,5 , b=-1/3 , -4a+3b=-4.2,5 + 3(-1/3)=-10-1=-11