Question

a){3x+y=7,20
{x+y=4,40

b){x+y=7
{x+2y=11

Answer 1

A)x+y=4,40
    y=4,40-x
   3x+y=7,20
   3x+(4,40-x)=7,20
   2x=7,20-4,40
   2x=2,80
    x=1,40 e y=3




B)x+y=7
   x=7-y
   7-y+2y=11
    7+y=11
      y=4     e x=3