The old mean was 51 now the mean is 42.33... (round that to 42) 51 - 42 = 9
The answer is 19
First you must set up the equation
÷
First, you must make the mixed number a improper fraction
÷
Then you must divide

Finally, simplify
19
Answer:
20days
Step-by-step explanation:
1 bag feed : 5/2 = 2.5 days
8 bags feed : 2.5*8 = 20 days
I worked them out on paper. I hope this helps. There’s a picture of the work.