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? Pick one
A) 40 days
B) 20 days
C) 30 days
D) 60 days
E) 40 days
30 days   30 days   30 days = 1/5 – 1/6 = 1/30 =&gt; 30 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?