Paul uses 1 can of frosting to frost a layer cake.  He uses a half can of frosting for a single cake, or a single pan of brownies, or a dozen cupcakes.  For Saturday, he needs to have 3 layer cakes, 6 dozen cupcakes, 12 single cakes and 18 pans of brownies ready and frosted for customer pick up.  How many cans of frosting will he need?
He needs 1 can of frosting per layer cake and he needs to make 3 layer cakes so that's 1*3 = 
<gadget id="calculator">1*3</gadget>
<output>3</output>
3 cans of frosting.
There are 6 dozen cupcakes,12 single cakes and 18 pans of brownies for a total of 6+12+18 = 
<gadget id="calculator">6+12+18</gadget>
<output>36</output>
36 orders.
Each of the 36 orders needs 1/2 can of frosting so they need 36*.5 = 
<gadget id="calculator">36*.5</gadget>
<output>18</output>
18 cans of frosting.
He needs 3 cans of frosting for the layer cakes and 18 cans for the remaining items for a total of 3+18 = 
<gadget id="calculator">3+18</gadget>
<output>21</output>
21 cans of frosting.

<result>21</result>