Check the attached photo for references.

In order to get the height of the window sill, we will analyze the given.

There is an angle, its hypotenuse and we need to find it's opposite side. 
That is equivalent to Sine. Therefore, we will get x by using the sine identity with respect to sides.

sin67= \frac{opposite}{hypotenuse} =\frac{x}{40}

Do the necessary transposition in order to isolate x to get the final answer.

If you're having trouble coming up with an answer, don't hesitate to message me. Good luck!