David found $12 on the street. He then gave it to his friend Evan who has $1 and needed to buy a watch worth $20. How much does Evan still need?
The total amount Evan has is $1 + $12 = $
<gadget id="calculator">1+12</gadget>
<output>13</output>
13.
So Evan still needs $20 - $13 = $
<gadget id="calculator">20-13</gadget>
<output>7</output>
7.

<result>7</result>