I will set up a solution for you, and then you take it from there. First, try drawing a diagram of the situation. Let x be the distance from the second position to the mountain, and let h be the height of the mountain. From the diagram you should be able to see that
h/(13 + x) = tan4°
h/x = tan10º
You have a system of 2 equations in 2 unknowns h and x. Now try to solve for h and x by elimination and finish from here.