Question : X can do a piece of work in 14 days, Y can do the same work in 28 days and Z can do it in 42 days. In how many days can X, Y, and Z together complete the work?

Question : x, y, and z are 3 values, such that x + y = 12, y + z = 17 and z + x = 19. What is the average of x, y, and z?

Question : A can complete a piece of work in 9 days. B and C can complete the same work in 12 days and 18 days respectively. If A, B, and C work together, then in how many days will they complete the work?

Question : If $x(x+y+z)=20$, $y(x+y+z)=30$, and $z(x+y+z)=50$, then the value of $2(x+y+z)$ is:

Question : If 4 men or 6 women can do a piece of work in 12 days, working 7 hours a day. How many days will it take to complete a work twice as large, with 10 men and 3 women working together 8 hours a day?