Aboy flying a kite lets out 150 feet of string that makes an angle of 64 degrees w/ the ground if the stringforms a straight line how high is the kite above the ground

I've drawn a diagram to help.
In the diagram, the side of the right triangle we're looking for is across from, or opposite, our 64° angle.  The 150 ft long string makes the hypotenuse of the right triangle formed.  Opposite/hypotenuse is the ratio for sine, so we set up the following equation:
sin 64 = x/150
Multiplying by 150 on both sides to cancel it, we have 
150 sin 64 = x
This comes out to 138 feet above the ground.