## Elementary Technical Mathematics

One common solution $\Rightarrow$ $(7,-5)$
We use the addition method below: We add the 2 equations: $x+2y=-3$ $2x+y=9$ Multiply both sides of the 1st equation by $-2$ to cancel $x$. $-2x-4y=6$ $\underline{+2x+y=9}$ $-3y=15$ Solve for $y$: $y=\frac{15}{-3}=-5$ Substitute into any of the 2 equations and solve for $x$: $x+2y=-3$ $x+2(-5)=-3$ $x-10=-3$ $x=10-3$ $x=7$