Billy can spit a watermelon seed 30 inches.  Madison can spit a watermelon seed 20% farther than Billy.  Ryan can spit a watermelon seed 50% shorter than Madison.  How far can Ryan spit a watermelon seed?
Madison can spit a seed 20% farther than Billy's 30 inches so that's .20*30 = 
<gadget id="calculator">20*.01*30</gadget>
<output>6</output>
6 inches farther.
Billy spits a seed 30 inches and Madison can spit 6 inches farther for a total of 30+6 = 
<gadget id="calculator">30+6</gadget>
<output>36</output>
36 inches.
Ryan can spit a seed 50% shorter than Madison's 36 inches for a total of .50*36 = 
<gadget id="calculator">50*.01*36</gadget>
<output>18</output>
18 inches.

<result>18</result>