Answer
(2, 6)
Work Step by Step
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.