How do you solve the system x-2y=8 and -x+3y=-5?

1) Substitution: $x - 2 y = 8 \setminus R i g h t a r r o w x = 2 y + 8 \setminus R i g h t a r r o w - \left(2 y + 8\right) + 3 y = - 5$
$\setminus R i g h t a r r o w y = 3 \setminus R i g h t a r r o w x = 6 + 8 = 14$ and the unique answer is the point $\left(x , y\right) = \left(14 , 3\right)$.
2) Elimination: add the two equations to get $y = 3$ and then substitute into, for example, the second equation to get $x = 3 y + 5 = 9 + 5 = 14$ so that the unique answer is the point $\left(x , y\right) = \left(14 , 3\right)$.