Hello from MrBillDoesMath!
Answer:
NONE of the provided answers.
Discussion:
a + b = 2a => (given)
(a - 2a) + b = 2a - 2a = 0 (subtract 2a from both sides)
-a + b = 0 =>
b - a =0
which is NONE of the provided answers.
Regards,
MrB
P.S. I'll be on vacation from Friday, Dec 22 to Jan 2, 2019. Have a Great New Year!