In one hour,a boat goes 21 km along the stream and 9…

In one hour,a boat goes 21 km along the stream and 9 km against the stream.The speed of the boat in still water (in km/hr) is :

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 #69017