Hi tanvirhossain,
When posting GMAT questions, you should make sure to do so in the appropriate Forum and you should post the FULL prompt (including the answer choices). For example, the Problem Solving (PS) Forum is here:
https://gmatclub.com/forum/problem-solving-ps-140/With this question, we are told that 12 identical sets of encyclopedias were sold which generated $1800 in commissions. This means...
$1800/12 = $150 of commissions per set
For that commission to equal 20% of the price of each set, we can set up the math in a number of different ways. Here's one option:
.2(Price) = $150
Price = 5($150) = $750 per set is the sell price.
GMAT assassins aren't born, they're made,
Rich
Contact Rich at: [email protected]www.empowergmat.com