John buys bags of popcorn for $4 and sells them for $8.  How much profit does he get by selling 30 bags?
Each bag makes a profit of 8-4=$
<gadget id="calculator">8-4</gadget>
<output>4</output>
4.
So he makes a total profit of 30*4=$
<gadget id="calculator">30*4</gadget>
<output>120</output>
120.

<result>120</result>