X+ y =5
3x-y=7
solve each system of equations by the addition method

X=3
Y=2
Use the "Guess and Check Method"
For example, I inputed 2 for X and found that it was too small to work for the second equation, so I put in 3. Then for Y, I input 2 because 3+2=5. I put 2 in to replace Y in the second equation (3x-y=7) to see that 9-2=7. Therefore, X=3 and Y=2

The answer is: a = about 63.59ft2 for 15