Question

− 3x − 30 = 5x + 18

−3x − 30 − 3x = 5x + 18 − 3x
− 30 = 2x + 18
−30 − 18 = 2x + 18 −18
− 48= 2x
Negative 48 over 2 equals 2x over 2
x=−24

Where is the error?

Answer 1

In the second and third line, where 3x was taken off both sides. On the left -3x-3x should have given -6x.
3x should have been added to both sides in order to cancel out the -3x