Annie was given a pack of crayons. The pack contained 21 crayons. She already had a box of 36 crayons in her locker. Her friend Bobby gave her half the amount she already had in her locker. She decided to give her sister Mary 1/3 of her total amount of crayons. How many crayons does she give to Mary?
Annie starts with 21 + 36 = 
<gadget id="calculator">21+36</gadget>
<output>57</output>
57 crayons.
Bobby ends up giving her 36 / 2 = 
<gadget id="calculator">36/2</gadget>
<output>18</output>
18 crayons.
Annie now has a total of 57 + 18 = 
<gadget id="calculator">57+18</gadget>
<output>75</output>
75 crayons.
She ends up giving Mary a total of 75 * (1 / 3) = 
<gadget id="calculator">75*(1/3)</gadget>
<output>25</output>
25 crayons.

<result>25</result>