Given a a right triangle, the length of any of the sides is obtained using the pythagoras theorem.
The pythagoras theorem states that the square of the length of the hypothenuse (the slant side) of a right triangle is equal to the sum of the squares of the lengths of the legs.
For the given triangle with legs, 9 and x and hypothenuse of 15.
Applying the pythagoras theorem we have:
[tex]9^2+x^2=15^2 \\ \\ x^2=15^2-9^2=225-81=144 \\ \\ x= \sqrt{144} =12[/tex]
Therefore, the value of x is 12.
