Question 629577
First lets find how far apart the ships are from the port in three hours. The first one is 60 (20*3) miles away from the port, and the other one is 45 (15*3) miles away from the port. If we sketch a picture:
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Then we can see that the distance from the two ships is the hypotenuse of a right triangle. If we apply Pythagorean's Theorem of a^2+b^2=c^2 and make a 45, and make b 60, then we can find out the answer. So 
2025+3600=c^2
5625=c^2
c=75
So the ships will be 75 miles apart at 2:30 pm.