The answer is 16
The Pythagorean theorem is a^2+b^2=c^2
You already have one side and the hypotenuse (c)
15^2+b^2=17^2
15^2= 225
17^2= 289
Now you have 225+b^2= 289
Subtract 225 from both sides and you get
b^2=64
Then take the square root of both sides to get b alone
b=8
Now, since the base of the inner triangle is half of the base of the pyramid, multiply your answer by 2
You will get 16
