Here's another mathantics video that teaches you how to divide fractions.
Summary
Fractions, just like any rational numbers, can be divided by each other. To divide fractions, we need to turn them into multiplication problems. You can magically do that using the reciprocal.
A reciprocal of a number is just the the number with its numerator and denominator flipped. If you have the number 53, its reciprocal will be 35. Integers, like 5, can be thought of as 15. Thus, their reciprocal will be 51.
So how can we turn division into multiplication? All we have to do is take the reciprocal of the second fraction. For example, suppose we have,
21÷23
We can turn this into a multiplication problem by replacing 23 with its reciprocal, 32.
21÷23→21×32
All you need to do now is multiply the numerators together and the denominators together.
21×32=2×31×2=62=31
So,
21÷23=31