First, lets write the angles in decimal form:
Now, notice that the sum of these two angles gives us a right angle:
Next, we have to find out how many miles they traveled after the 4 hours, then, we have the following:
therefore, the triangle of the picture is a right triangle with the following meausres:
using the pythagorean theorem, we get the following:
therefore, after 4 hours, the boats are 127.2 miles apart