Subtract 9 twice.
24-9-9 = 6
Half of 6 is 3, so 3 is the width since adding it twice and adding the length twice gives perimeter.
The way to find Volume is V=lwh so plug in the length, width and height( V=(10)x(2/3)x(9) ) and you'll get your answer.
To transform it into percent we want to have 100 into denominator. The easiest way is divide numerator and denominator by 3 (thats because than it doesnt change the value of fraction), so:

- its the result