In the general case, you have two choices. Isolate one unknown in one of the equation and substitue in the other, or remove one unknown from one of the equation by adding a multiple of the other.
In your case, we will only do the first method because the second equation has only one unknown, x. We isolate it :
[tex]x = \frac{ - 57}{2} [/tex]
You replace in the other equation x by its new value, which yields
[tex] - 7 \cdot\frac{ - 57}{2} + 6y = - 5[/tex]
You just have to isolate y :
[tex]y = - \frac{5}{6} - \frac{133}{4} = - \frac{409}{12} [/tex]
If the +47 in the second equation was meant to be +4y... well... It is a different story. Use the first method I described (substitution). It is similar to what I detailed.
