Okay, here we have this:
Considering the provided information, we are going to identify which equation can Bob use to find the value of x, so we obtain the following:
We want to know an angle from the measure of the opposite leg and the adjacent leg, and the trigonometric ratio that relates these data is the tangent. Then substituting in the formula of the tangent we have:
Replacing:
Finally we obtain that the correct answer is the second option.