Question 1032755
this question can be solved through ratio and proportion so
Labours     rooms       Days
30            15         18
12            12          x

Days and labours have inverse proportion and days and rooms have direct proportion. so
 
(30/12) x (12/15) = x/18

2.5 x 0.8 = x/18
2 = x/18
x = 18 x 2
x = 36 days