What is three quarters of 24?

To figure that out you first ask, "What number is three fourths of twenty-four?"

Then you have to turn that question into an equation. To do this, you break down the question into parts:

What number | is | 3/4 | of | 24

In algebraic equations, "is" means "equals" and "of" means "times". So you can insert those into the equation to make it mathematically understandable:

What number = 3/4 x 24

Then you designate "What number" as N, and you have a proper equation:

N = 3/4 x 24

Now you multiply on the right side of the equation to get

N = 18

Now if you return to the sentence, you can replace "What number" with "eighteen":

Eighteen is three fourths of twenty-four.