Emmett does 12 jumping jacks, 8 pushups, and 20 situps. What percentage of his exercises were pushups?
First find the total number of exercises Emmett does: 12 jumping jacks + 8 pushups + 20 situps = 
<gadget id="calculator">12+8+20</gadget>
<output>40</output>
40 exercises.
Then divide the number of pushups by the total number of exercises and multiply by 100% to express the answer as a percentage: 8 pushups / 40 exercises * 100% = 20%

<result>20</result>