The Pythagorean theorem is all about solving the missing apart on a right triangle. Usually the missing part are the legs and the hypotenuse. The formula for the Pythagorean theorem is a^2+b^2=c^2
You are given 2 side length and need to find all 3 side on the right triangle. The easy way to remember the c is always the hypotenuse and a and b are the legs.
To solve this right triangle you need to use the pythagorean theorem formula. a^2+b^2=c^2 the legs are 9 and 7 and the hypotenuse x. You plug it in 7^2+9^2=x^2 it equal to 49+81=x^2, next you add them 130=x^2 then the next thing is you square root both of them √(130=√(x^2 once you square root it will be x=11.4 but always round it to the nearest hundredth 11.401. Once it done you put it back to the triangle and should be 11.4ft don't forget your units also.