What is the principal sum

What is the principal sum? I. The sum amounts to Rs. 720 in 4 years at S.I. II. The sum amounts to Rs. 810 in 7 years at S.I. III. The rate of interest is 10% p.a.

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 #49435