A and B can do a piece of work in 5 days, B and C in 6 days, C and A in 7 days. How long will C take to do it?  Select.
A) 260/19 days B) 240/23 days C) 220/17 days D) 200/19 days E) 180/11 days
2c = 1/6 + 1/7 – 1/5 = 23/210   c = 23/240 =&gt; 240/23 days   The answer is 240/23 days.
<result>B</result>
A and B can do a piece of work in 5 days, B and C in 6 days, C and A in 7 days. How long will C take to do it?