# How do you solve y= 4x + 45 and x= 4y?

Oct 4, 2015

$x = - 12$, $y = - 3$
Knowing that $x = 4 y$, you can write the first equation as
$y = 4 \left(4 y\right) + 45 \to y = 16 y + 45 \to - 15 y = 45$, isolating the $y$-terms by bringing them all to the left. Now, solving by $y$, we have $y = - 3$.
Since $x$ was $4 y$, we know that $x = 4 \cdot \left(- 3\right)$, and thus $x = - 12$ and the system is solved.