Don't you understand how to do it?

1, find the fraction of a number, which can be divided by several (denominator).

For example:

What is a quarter of 12?

Formula: 12÷4=3

A quarter of 12 is 3.

2. Ask for a fraction of a number, which can be divided by the denominator and then multiplied by the numerator.

For example:

How much is five sixths of 48?

Formula: 48÷6×5=40

Five sixths of forty-eight is forty.