Answer:
18.5
Explanation:
You want the length x of the leg in a right triangle that is opposite an angle of 51°, given the adjacent leg is 15 units.
Tangent
The tangent ratio is ...
Tan = Opposite/Adjacent
In this triangle, that means ...
tan(51°) = x/15
Multiplying by 15, we have ...
x = 15·tan(51°)
x ≈ 18.5 . . . units