Answer:
Step-by-step explanation:
Here's how you convert:
![\sqrt[n]{x^m}=x^{\frac{m}{n}](https://tex.z-dn.net/?f=%5Csqrt%5Bn%5D%7Bx%5Em%7D%3Dx%5E%7B%5Cfrac%7Bm%7D%7Bn%7D)
The little number outside the radical, called the index, serves as the denominator in the rational power, and the power on the x inside the radical serves as the numerator in the rational power on the x.
A couple of examples:
![\sqrt[3]{x^4}=x^{\frac{4}{3}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7Bx%5E4%7D%3Dx%5E%7B%5Cfrac%7B4%7D%7B3%7D)
![\sqrt[5]{x^7}=x^{\frac{7}{5}](https://tex.z-dn.net/?f=%5Csqrt%5B5%5D%7Bx%5E7%7D%3Dx%5E%7B%5Cfrac%7B7%7D%7B5%7D)
It's that simple. For your problem in particular:
![\sqrt[3]{7}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B7%7D)
is the exact same thing as ![\sqrt[3]{7^1}=7^{\frac{1}{3}](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B7%5E1%7D%3D7%5E%7B%5Cfrac%7B1%7D%7B3%7D)
The boy would have 3 brothers and 3 sisters therefore in the family there would be 4 boys and 3 girls
