you can multiply the top equation by 3, then both y's are cancelled or zeroed out. You add -21 and 6 to get -15x. Than you add 42 and 18 to get 60. So, -15x=60 and from there you do 60/-15 to get x=-4. Plug in what you got for x into any of the two equations to get y, which is 7.
