I put this question on the board the other day as I found it interesting. The idea is students find the area of the triangle. It looks like a right angled triangle, and sure enough a lot of students assumed that it was.
One or two tested it using Pythag, and found it wasn’t. Those who tested it, applied the cosine rule to find an angle, and found the area using 1/2abSinC.
Those who were less meticulous, jumped straight into 1/2 base x height.
Interestingly, the answer sheet lists it as this:
However, this is taken from a “Using Sine to find Area” worksheet, so students would likely have used the context to not use 1/2 base x height.
If I were less experienced however, I might be inclined to let those assuming this was a right angled triangle off the hook, as that gives an answer of 85.
The other way gives a decimal that rounds to 85. Don’t just rely on an answer sheet!