Question 332755
Since 5 machines produces 12 gallon in 10 days, this means they produce 

12/10=1.2 gallons per day.

Thus, each machine produces 1.2/5=.24 gallons per day.

Therefore, 4 machines produce 4(.24)=.96 gallons per day.

So, it takes the 4 machines 48/.96=50 days to produce 48 gallons.