Sides Reversed Is Puzzle

The Puzzle:

Sides Reversed Is
Hungry Horace was copying down his Mathematics Homework the other day, but because he was in a rush (he wanted to be first in the dinner queue) he copied it down incorrectly.

They had been learning about multiplying 2 digit numbers, and had five questions to do at home. Horace, however, copied every number down backwards:

Instead of writing 12 x 42 Horace wrote 21 x 24

Instead of writing 12 x 84 Horace wrote 21 x 48

Fortunately for Horace, all his answers were still correct!

What were the other three questions?
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