Question

The sum of two numbers is 3. Their difference is -5. What are the two numbers?

Answer 1

X + y = 3
x - y = -5

We can solve using substitution
x + y = 3
subtract x to isolate y
y = 3 - x
substitute it into the second expression
x - y = -5
x - 3 + x = -5
combine like terms
2x - 3 = -5
add 3 to both sides
2x = -2
divide both sides by 2
x = -1

now to find y

x + y = 3
-1 + y = 3
add 1 to both sides
y = 4