Isaac cut his 30 meters ribbon into 6 equal parts. He then used 4 parts of the ribbon. How many meters of ribbon are not used?
Each part is 30/6 = 
<gadget id="calculator">30/6</gadget>
<output>5</output>
5 meters long.
Since Liam used 4 parts, then he used 5 x 4 = 
<gadget id="calculator">4*5</gadget>
<output>20</output>
20 meters of the ribbon.
So, 30 - 20 = 
<gadget id="calculator">30-20</gadget>
<output>10</output>
10 meters of ribbon is not used.

<result>10</result>