X,Y and Z together can complete a job in 10 days.

As rate is given so lets assume some smart numbers for the number of days required by each to complete the work.

Let \(z\) complete the work in \(12\) days so \(y\) will do it in \(6\) days and \(x\) will do it in \(2\) days (as rate of \(x=3*\)rate of \(y\); and rate of \(y=2*\)rate of \(z\)

So \(x+y+z\) together will do it in \(= \frac{1}{2}+\frac{1}{6}+\frac{1}{12}=\frac{9}{12}\)

or together they will take \(\frac{12}{9}\) days

but it is given that they took \(10\) days

So, together they took \(\frac{12}{9}\) days, when \(z\) took \(12\) days alone to do the work

Hence together when they took \(10\) days then \(z\) will take \(=\frac{12}{12/9}*10=90\) days

Option C