17 yards. The fence that enclose Sondra's backyard is a right triangle whose sides measuring 8 yards, 15 yards and 17 yards respectively.
The key to solve this problem is using the Pythagorean Theorem that dictates; In every right triangle the square of the hypotenuse is equal to the sum of the squares of the legs and the equation hypotenuse²=leg1²+leg2².
For this problem we know the measuring of two side, which mean that we can apply Pythagorean Theorem equation as follow:
Let's say that one of the side is a = 8yards, and the other side is b = 15yards. So, we want to know how long the third side c long.
Applying the Pythagorean Theorem:
Substituting the values of the sides a and b: