The cross-section of a cannel is a trapezium in shape

The cross-section of a cannel is a trapezium in shape. If the cannel is 11 m wide at the top and 9 m wide at the bottom and the area of cross-section is 960 sq m, the depth of cannel 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 #4169