X, Y and Z can do a piece of work in 46 days, 92 days and 23 days, respectively. X started the work. Y joined him after 2 days. If Z joined them after 8 days from the beginning, then for how many days did X work?

Answer: Option C

2 days work of X = 2 × 2 = 4
After Y joined X and Y work 6 days = 3 × 6 = 18
After 8 days from begging - X, Y and Z work together $$=\frac{92-22}{7}=\frac{70}{7}=10\text{ days}$$
Total days work of X = 10 + 8 = 18 days