Answer:
10 days
Step-by-step explanation:
Mr Datu can pay 8 workers for 15 days,
Then at the same rate he can pay 1 worker for the number of days = 15×8
= 120
If he adds number of workers = 4
Then total number of workers = 8 + 4 = 12
With the same rate Mr Datu can pay 12 workers for number of days = 
= 10 days
Therefore, Mr Datu can pay 12 workers for 10 days a the same rate.
No because then somewhere in the problem you could multiply once more. like if u had 234 as ur answer, but had 2 as a remainder, u would change the 4 to a 5 (don't know if tht math is right, but the main idea of it is right)
The first blank is 21 and the second is 37