A fast-food chain offers free delivery for a minimum purchase of $18. Danny ordered 2 quarter-pounder burgers for $3.20 each, 2 large fries that cost $1.90 each, and 2 milkshakes that cost $2.40 each. How much more worth of food should he order to avail of the free delivery?
Two quarter-pounder burgers cost $3.20 x 2 = $
<gadget id="calculator">3.20*2</gadget>
<output>6.4</output>
6.40.
Two large fries cost $1.90 x 2 = $
<gadget id="calculator">2*1.9</gadget>
<output>3.8</output>
3.80.
Two milkshakes cost $2.40 x 2 = $
<gadget id="calculator">2*2.4</gadget>
<output>4.8</output>
4.80.
The total amount spent for the burgers, fries, and shakes is $6.40 + $3.80 + $4.80 = $
<gadget id="calculator">6.4+3.8+4.8</gadget>
<output>15</output>
15.
Therefore, he should order $18 - $15 = $
<gadget id="calculator">18-15</gadget>
<output>3</output>
3 worth of additional food to take advantage of the free food delivery.

<result>3</result>