I think it’s 17 cause 51/3 is 17.
We are given the following expression:
![\sqrt[3]{875}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B875%7D)
We can factor 875 as:
![\sqrt[3]{125\times7}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B125%5Ctimes7%7D)
Now we will use the following property:
![\sqrt[x]{a\times b}=\sqrt[x]{a}\times\sqrt[x]{b}](https://tex.z-dn.net/?f=%5Csqrt%5Bx%5D%7Ba%5Ctimes%20b%7D%3D%5Csqrt%5Bx%5D%7Ba%7D%5Ctimes%5Csqrt%5Bx%5D%7Bb%7D)
Applying the property:
![\sqrt[3]{125}\times\sqrt[3]{7}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B125%7D%5Ctimes%5Csqrt%5B3%5D%7B7%7D)
Solving the cubic root on the left:
![5\sqrt[3]{7}](https://tex.z-dn.net/?f=5%5Csqrt%5B3%5D%7B7%7D)
Since we get simplify any further this is the answer.
(x - 8)^2 = 144
take the sq rt of both sides
x - 8 = 12
x = 12 + 8
x = 20
20 feet by 20 feet
9 mile... you didn't really give enough info.