A and B can do a piece of work in 7 days. With the help of C they finish the work in 5 days. C alone can do that piece of work in?
Choose the correct choice from the following choices.
A) 15.5 days
B) 19.5 days
C) 17.5 days
D) 16.5 days
E) 18.5 days
17.5 days = 1/5 – 1/7 = 2/35 =&gt; 17.5 days   ANSWER:17.5 days
<result>C</result>
A and B can do a piece of work in 7 days. With the help of C they finish the work in 5 days. C alone can do that piece of work in?