Question

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

Answer 1

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