A vampire drains three people a week. His best friend is a werewolf who eats five people a week, but only fresh ones, never drained ones. How many weeks will a village of 72 people last them both?
The vampire and werewolf need 3 + 5 = 
<gadget id="calculator">3+5</gadget>
<output>8</output>
8 people a week.
A village of 72 people will last them both 72 / 8 = 
<gadget id="calculator">72/8</gadget>
<output>9</output>
9 weeks.

<result>9</result>