x dollars
Note: You can multiply anything by 1. If 4 quarters = 1 dollar, then 4 quarters / 1 dollar = 1.
So we can do this:
x dollars * 1
x dollars * (4 quarters / 1 dollars)
(yeah, I know, "1 dollars," don't worry about plural vs singular)
Take the 4 and 1 out like this:
(4/1) * x dollars * (quarters / dollars)
4x dollars * (quarters / dollars)
The dollars cancel out, leaving you with:
4x quarters
So, if you have x dollars, then you have 4x quarters
x dollars = 4x quarters