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

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