Solve the system.
$ \left\{ \begin{tabular}{l} $ y = x + {\color{red}-2} $ \\ $ y = -{\color{red}3} x + {\color{red}10} $ \end{tabular} \right. $
The TeX makes it hard to read, but it appears you want to solve
y = x + 2
y = -3x + 10
If that's so, then just substitute the 1st value for y into the 2nd equation:
x+2 = -3x+10
4x=8
x=2
so, y=4