Mike wants to buy a new phone. The cost of the phone is $1300. How much more money does Mike need if he already has 40% of the amount he needs?
Mike already has 40/100 * 1300 = $
<gadget id="calculator">40/100*1300</gadget>
<output>520</output>
520.
This means he needs 1300 - 520 = $
<gadget id="calculator">1300-520</gadget>
<output>780</output>
780 more, to buy the phone.

<result>780</result>