By selling 12 pens for a rupee a woman loses 20%

By selling 12 pens for a rupee a woman loses 20%. How many for a rupee should he sell in order to gain 20%?

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 #5356