Question

please tell me answer of third question

Answer 1

you have to use the Pythagoras Theorem only

Answer 2

Hey"

Here is your answer friend.

h=15m.
p=12m

By pythagoras theorem

h2=p2+b2
(15)2=(12)2+b2
225=144+b2
225-144=b2
81=b2
b=9

here a=b=9

hope it is helpful to you.