Answer:
21
Step-by-step explanation:
Find out all the combinations
3 0 + 3 = 3 Reversed 30
12 1 + 2 = 3 21
21 2 + 1 = 3 12 <-----------------
30 3 + 0 = 3 3
Then consider what the Question is Asking
And apply it to each of the combinations
Then Use trial and error to find the answer