Brittney can chop 15 onions in 5 minutes. Carl can chop 20 onions within that same time. How many more onions can Carl chop in 30 minutes than Brittney?
Brittney can chop 15/5 = 
<gadget id="calculator">15/5</gadget>
<output>3</output>
3 onions in one minute.
Carl can chop 20/5 = 
<gadget id="calculator">20/5</gadget>
<output>4</output>
4 onions in one minute.
Brittney can chop 3 x 30 = 
<gadget id="calculator">3*30</gadget>
<output>90</output>
90 onions in 30 minutes.
Carl can chop 4 x 30 = 
<gadget id="calculator">4*30</gadget>
<output>120</output>
120 onions in 30 minutes.
Carl can chop 120 - 90 = 
<gadget id="calculator">120-90</gadget>
<output>30</output>
30 more onions than Brittney in 30 minutes.

<result>30</result>