Every day, Billie bakes 3 pumpkin pies for 11 days and puts them in the refrigerator.  It takes 2 cans of whipped cream to cover 1 pie.  If Tiffany comes over and eats 4 pies, how many cans of whipped cream does Billie need to buy to cover the remaining pies?
In total Billie bakes 3 x 11 = 
<gadget id="calculator">3*11</gadget>
<output>33</output>
33 pies.
After Tiffany eats the pies, this many pies are in the refrigerator: 33 - 4 = 
<gadget id="calculator">33-4</gadget>
<output>29</output>
29 pies.
She needs to buy this many cans of whipped cream 29 x 2 = 
<gadget id="calculator">29*2</gadget>
<output>58</output>
58 cans.

<result>58</result>