There are 45 children in a classroom. One-third of them are girls. How many boys are in the classroom?
One-third of all the kids are girls, which means 1/3 * 45 = 
<gadget id="calculator">1/3*45</gadget>
<output>15</output>
15 children.
So there are 45 - 15 = 
<gadget id="calculator">45-15</gadget>
<output>30</output>
30 boys in the classroom.

<result>30</result>