Suppose a - b = 0a-b=0a, minus, b, equals, 0. Which one of these expressions equals a+ba+ba, plus, b?

First we have the following equation:

a - b = 0

We clear one of the variables depending on the other:

a = b

Therefore we have to for the following expression:

a + b

We can substitute one of the variables, obtaining:

a + a = 2a

Equivalently:

b + b = 2b

Answer:

a + b = 2a

or

a + b = 2b