Find the length of x for a trangle with sides 17 and 8. Express your answer in simplified radical form.?

Question

The answer in the book says 15, but Im not sure how to get that

Answer 1

is there any given angle?
I think this triangle is a right angled triangle.
Because 17^2=8^2+15^2

Therefore,
17^2=x^2+8^2
x^2=289-64
=225
x=15

Answer 2

You know what, if the problem has been stated as is without any figure, so your best assumption is that you are given a right triangle so you can use the Pythagorean theorem.

a^2 + b^2 = c^2

where :
c = hypotenuse
a, b = two other shorter sides

Since the answer is 15, it is obvious that the x = one of the shorter side not the hypotenuse.

Let x = a = unkown
b = 8
c = 17

From the Pythagorean formula :

a^2 + b^2 = c^2
a^2 = c^2 - b^2
a = ( c^2 - b^2 )^1/2
a = ( 17^2 - 8^2 )^1/2
a = ( 289 - 64 )^1/2
a = ( 225 )^1/2
a = 15

Note : (___)^1/2 = means taking the
square root