Answer:
The missing side is 8 ft long
Explanation:
According to Pythagoras theorem "It states that the area of the square whose side is the hypotenuse is equal to the sum of the areas of the squares on the other two sides"
mathematically it is stated as

Given that
c, hypotenuse= 17 ft
a = 15 ft
b= ?
Applying the Pythagoras theorem formula by inserting our given parameters and solving for b we have

Making b subject of formula we have

Square root both sides we have

Hence the missing side is 8 ft long