Let one number = x
Let the other = y
2x + 3 = y (1)
x + y = 57 (2)
work with the top equation get the y on the left and the 3 on the right
2x + 3 = y Subtract 3 from both sides.
2x + 3 - 3 = y - 3 Combine
2x = y - 3 Subtract y from both sides.
2x - y = y - y - 3 Combine on the right
2x - y = - 3 (3) Add (3) and (2) together.
x + y = 57
3x = 54 Divide by 3
3x/3 = 54/3 Do the division
x = 18
Find y
x + y = 57 Substitute for x
18 + y = 57 Subtract 18
18 - 18 + y = 57 - 18 Combine
y = 39
Answer
x = 18
y = 39