Answer:
30 days
Step-by-step explanation:
3/10 is completed in 9 days, so 6/10 in 18 days and 9/10 in 27 days.
If it only takes 9 days for 3/10, then 9 divided by 3 = 3. The final 1/10 is completed in 3 days. This all equals 30 days.
I could be wrong, but that's what I think.