Cindy has 37 envelopes. If Cindy gives 3 envelopes to each of her 5 friends, how many envelopes does she have left?
Cindy gave 3 envelopes/friend x 5 friends = 
<gadget id="calculator">3*5</gadget>
<output>15</output>
15 envelopes to her friends.
Cindy has 37 envelopes - 15 envelopes = 
<gadget id="calculator">37-15</gadget>
<output>22</output>
22 envelopes left.

<result>22</result>