
Frank C. answered 01/03/18
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So you want to charge the customer $23.20
Let the cost for you = C
$23.20 = C + 10% of C
= C + 10% × C
= C + 0.1 × C
= 1.1 × C
C = 21.090909...... ≈ $21.09
If I understand your question, your customer is only willing to pay what your cost was plus 10%. Since you want them to pay $23.20, you should say it cost you $21.09 because if you add 10% to that, it will come out as 23.199 on the calculator, and they'll oblige to paying $23.20