Solve the system:
3x-y-7=0
x+5y+3=0
Couple ways to do this. One is as follows.
1) Solve the first equation for x.
2) Take the value you just found for x and substitute it for every x in the second equation.
3) Solve the second equation for y.
You now have a numeric value for y. You have half done.
4) Pick either original equation and substitute the value for y just found.
5) Solve the equation for x.