## Algebra 1: Common Core (15th Edition)

We know that y=3x. Thus, in the first equation, wherever we see y, we will substitute 3x, and then we will solve: $x+3x =8 \\\\ 4x =8 \\\\ x=2$ We now substitute x back in: $y=3(2)=6$ We plug (2,6) back into the first equation and confirm that our answer is, indeed, correct.