Answer:
x = -4, y = 2
Step-by-step explanation:
[tex]\left\{\begin{array}{ccc}5x+15y=10\\5x-10y=-40&\text{change the signs}\end{array}\right\\\underline{+\left\{\begin{array}{ccc}5x+15y=10\\-5x+10y=40\end{array}\right}\qquad\text{add both sides of the equations}\\.\qquad\qquad25y=50\qquad\text{divide both sides by 25}\\.\qquad\qquad\boxed{y=2}\\\\\text{Put the value of y to the first equation:}\\\\5x+15(2)=10\\5x+30=10\qquad\text{subtract 30 from both sides}\\5x=-20\qquad\text{divide both sides by 5}\\\boxed{x=-4}[/tex]
