Hello,
For this problem, we will use cosine which is adjacent over hypotenuse. They want you to solve for the hypotenuse.
cos(56.76) = 56.76/x (multiply both sides by x)
x cos(56.76) = 56.76 (divide both sides by cos(56.76))
x = 103.548816..
x = 103.5
Your final answer approximately x = 103.5.