You would divide because to find a percent, you can use a equation. Like
A=PW
A= Part = $6
P= Percent = x (unknown)
W= Whole = $15
Equation= 6= 15x.
To figure out x you have to isolate it so you would divide because the inverse operation of multiply is divide and you have to divide 15 on both side. 6 divided by 15 is 0.4. 0.4 is equal to 40%
