Matt and Peter can do together a piece of work in 20 days. After they have worked together for 12 days Matt stops and Peter completes the remaining work in 8 days. In how many days Peter complete the work separately.
Pick one.
A) 21
B) 24
C) 20
D) 25
E) 30
Together they complete the job in 20 days means they complete 12/20 of the job after 12 days.   Peter completes the remaining (8/20) of the job in 8 days which means that the whole job(1) can be completed in X days.   X=8/(8/20)= 
<gadget id="calculator">8/(8/20)</gadget>
<output>20</output>
20   20
<result>C</result>
Matt and Peter can do together a piece of work in 20 days. After they have worked together for 12 days Matt stops and Peter completes the remaining work in 8 days. In how many days Peter complete the work separately.