DS8's first "written math proof".

Question: Genet multiplied a 3-digit number by 1002 and got AB007C, where A, B, and C stand for digits. What was Genet's original 3-digit number?

DS8's answer (I transcribed his exact words): The answer is 539. y=3 because in the 7C, 3+3 is 6, Z has to be a number 5 - 9 to make the 6 a 7. x is 5 because the number under 2x is a 0, so it has to be 10 no matter what. 10 divided by 2 is 5 so x is 5. The number under Z is zero, but since the 2x is added up to a 10, z has 1 more, so z has to be 9. so xyz = 539.