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.
Choices:
A) 21
B) 24
C) 20
D) 25
E) 30

Rationale: "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 ) = 20 c"
Answer: C