In order to solve the simultaneous equations, you should first get rid of one of the unknowns. In this case, one of the ways to do this is to multiply both sides of the first equation by 5 (2x+3y=17 => 10x+15y=85) and then subtract the second equation from the first one in order to get rid of the x: (10x+15y)-(10x-y)=(85)-(5) => 16y=80 => y=5. Having found y, we can substitute for y=5 in the second equation to find x: 10x-5=5 => 10x=10 => x=1. Hence, we get x=1, y=5.