Question

Solve the system of equations by graphing 4x-5y=20

Answer 1

Here is your graph of the system. Where they cross is the answer, which is -4. Pretty much you have to graph each equation and where they meet is the answer.

Answer 2

And doing some vandalizing to the posted image by MathJot, check the picture below.

$\bf \begin{cases} 4x-5y=20\\ 3x+y=-4 \end{cases}\\\\ -------------------------------\\\\ 4x-5y=20\implies 4x-20=5y\implies \cfrac{4x-20}{5}=y\\\\\\ \boxed{\cfrac{4x}{5}-4=y} \\\\\\ 3x+y=-4\implies \boxed{y=-4-3x}$