I think the answer is 1,161 feet
Sorry if that’s incorrect, but here’s the explanation in case you need it:
The tangent of a triangle is the opposite leg over the adjacent leg. 311 is the opposite leg, and X would be the adjacent leg. So 311 divided by x is equal to tan 15. If we rearrange this to be equal to X, X equals 311 divided by tan 15. Tan 15 is equal to 0.2679, so 311/0.2679 = 1,160.6. That amount rounds up to 1,161, giving you the answer of 1,161 feet.
