x + y = 16
x - y = -8
Step 1) Choose two random numbers between -12 and 12 (4 and 12 in this case).
Step 2) Let one of the numbers be x and the other be y.
Step 3) Add both numbers together to form 1 equation.
Step 4) Subtract one number from another to form the other equation.
And with that, we are done.