Dividing by a fraction is the same as multiplying the reciprocal of the fraction. What is the reciprocal of a fraction? It's essentially the same fraction, just the numerator and denominator switching places (flipping the fraction upside down). Knowing this, the following is true:
![5/\frac{1}{3} = 5*\frac{3}{1}](https://tex.z-dn.net/?f=5%2F%5Cfrac%7B1%7D%7B3%7D%20%3D%205%2A%5Cfrac%7B3%7D%7B1%7D)
We also need to know that whenever the denominator of a fraction is 1, the fraction is equal to the numerator itself. Knowing this, the following is also true:
Applying this to the first concept, we can say that:
![5*\frac{3}{1} = 5*3](https://tex.z-dn.net/?f=5%2A%5Cfrac%7B3%7D%7B1%7D%20%3D%205%2A3)
I hope this helps!