First we must isolate one of the variables (x or y) in one of the equations (First or second). Here I'll isolate y in equation 2 since it's the easiest to solve.
Now that we have successfully isolated, we will next substitute the chosen variable (y) in the opposite equation (Eq 1) with the equation we have recently formed:
Next substitute x in the opposite equation: (basically the equation we previously used to create a new equation which is Equation 2)