^
always remember the pythagorean triple:
no need for the very long solution..
because.. the triple is 3,4,5
so 3 is the shortest leg, 5 is the hypotenuse and as follows..
so if 20 is the hypotenuse the triple will be 12,16 and 20.. why?? same as 3,4 and 5..
i just gave you a short tip.. because in math quiz shows.. 5 seconds is enough for that question to know the two legs..
(based on experience.. haha)