To solve this (assuming that you are using a graphing calculator of some sort) you have to first isolate x since that is what you are solving for. First, you multiply both sides by x to get x on the numerator to make it easier to solve. This would look something like this: x(Cos 55)=13
Then, to isolate x, you divide both sides by cos 55 leaving you with this: x= 13/cos55.
Then, you type 13/cos 55 (make sure your calculator is in degrees) and you get 22.66 (rounded to nearest hundredth)