To solve this one and future word problems, perhaps you might start with verbal equation tat you then convert into a mathematical one. Such as:
20% of what amount of sales will result in a $1,000 commission?
.20 X = $1,000
Divide each side of the equation by .20 to clear the left side, leaving only the "X".
.20 X
____ = $1,000/.20
.20
X = $5,000 commission
6th Grade Math Tutoring