Is this the right answer?

Hello from MrBillDoesMath!
Answer:
Yes!
Discussion:
a + b= 2a => subtract "a" from both sides
a - a + b = 2a - a => as (a-a) = 0 and (2a-a) = a
b = a (*)
Then from (*) above
b-a = b - b => b-b = 0
b -a = 0
Thank you,
MrB