Without working a quadratic equation, we can examine the divisors of 36 for a pair that add to 15.

1*36 = 36 1+36 = 37

2*18 = 36 2+18 = 20

3*12 = 36 3+12 = 15

Your two numbers are 3, 12

1*36 = 36 1+36 = 37

2*18 = 36 2+18 = 20

3*12 = 36 3+12 = 15

Your two numbers are 3, 12