arithmetic - 12 labours can complete a work in 18 days six days after they started working 4 labours joined them how many days will all of them take to finish the remaining work - skillgun

(12 * 18) labours can complete the work in 1 day.
1 labour's 1 days work = 1/216
12 labours 6 days work = (1/18)*6 = 1/3
Remaining work = 1 - (1/3) = 2/3
16 labours 1 days work = 16/216 = 2/27
2/27 work is done by them in 1 day.
2/3 work is done by them in (27/2)*(2/3) = 9 days.