Question

   A B
    x 3
C A B

Answer 1

As we need B at unit place and A at ten's places,
∴ B = 0 as 3 x 0 = 0
Now we want to find A, 3 x A = A (at unit's place)
∴  A = 5, as 3 x 5 = 15
∴  C = 1

   5 0
    x 3
 1 5 0