3 cloves of garlic can repel 2 vampires, 8 vampire bats or 3 wights. How many cloves of garlic are needed to repel 30 vampires, 12 wights and 40 vampire bats?
First find the total number of cloves needed to repel the vampires: 30 vampires * 3 cloves / 2 vampires = 
<gadget id="calculator">30*3/2</gadget>
<output>45</output>
45 cloves.
Then find the total number of cloves needed to repel the wights: 12 wights * 3 cloves / 3 wights = 
<gadget id="calculator">12*3/3</gadget>
<output>12</output>
12 cloves.
Then find the total number of cloves needed to repel the vampire bats: 40 vampire bats * 3 cloves / 8 vampire bats = 
<gadget id="calculator">40*3/8</gadget>
<output>15</output>
15 cloves.
Then add up these three amounts to find the total number of cloves needed: 45 cloves + 12 cloves + 15 cloves = 
<gadget id="calculator">45+12+15</gadget>
<output>72</output>
72 cloves.

<result>72</result>