eg. x is the first number, y is the second number
The equation
x - y = 3
x² + y² = 65
Use subtitution to find y
x - y = 3
x = y + 3
x² + y² = 65
(y + 3)² + y² = 65
y² + 6y + 9 + y² = 65
2y² + 6y - 56 = 0
y² + 3y - 28 = 0
(y + 7)(y - 4) = 0
y = -7 or y = 4
Find x with y
If y = -7
x = y + 3
x = -4
If y = 4
x = y + 3
x = 7
So the numbers are 7 and 4, or -7 and -4