Question

Let 2x-5y=16 and 5x+3y=9. what is the value of 12x+y

Answer 1

2x-5y=16    =>10x-25y=80
5x+3y=9     => 10x+6y=18
subtract one from the other: (6-(-25)y=(18-80), 31y=-62, y=-2
plug y=-2 in 2x-5y=16 to find x: 2x+10=16, x=3
12x+y=12*3-2=34