Kate bought 7 packs of red bouncy balls and 6 packs of yellow bouncy balls. Each pack contained 18 bouncy balls. How many more red bouncy balls than yellow bouncy balls did Kate buy?
Kate bought 7 packs * 18 balls/pack = 
<gadget id="calculator">7*18</gadget>
<output>126</output>
126 red bouncy balls.
She also bought 6 packs * 18 balls/pack = 
<gadget id="calculator">6*18</gadget>
<output>108</output>
108 yellow bouncy balls.
Kate bought 126 balls - 108 balls= 
<gadget id="calculator">126-108</gadget>
<output>18</output>
18 more red bouncy balls than yellow bouncy balls.

<result>18</result>