Because this is a right triangle, we can use a trigonometric function to solve for the missing side.
Remember: SOH-CAH-TOA
We are given an angle, as well as the adjacent side and hypotenuse. Therefore, we should use the cosine function to solve for x.
cos(67) = x / 15
x = cos(67) * 15
x = 5.9
Answer: 5.9
Hope this helps!
