Question
X can work as fast as Y and Z together. X and Y together
can finish the same task 3 times as fast as Z. If all three working together can finish the task in 18 days, how many days, will Z take to finish the task?Solution
Let the number of days it takes. X to finish the task be x Y to finish the task be y Z to finish the task be z Therefore, as per the given relations 
By adding the first two equations, we get 
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