In a division sum, the remainder is 0

In a division sum, the remainder is 0. As student mistook the divisor by 12 instead of 21 and obtained 63 as quotient. What is the correct quotient ?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #19496