Question

the sum of two numbers is 8 if one number is subtracted from the other the result is -4

Answer 1

a + b = 8
a - b = -4

a = b - 4
(b - 4) + b = 8
2b - 4 = 8
2b = 12
b = 6
a + 6 = 8
a = 2

a = 2
b = 6

2 + 6 = 8
2 - 6 = -4

Answer 2

Use these formulas:

x + y = 8
x - y = -4