For this case we must find the product of two mixed numbers:

So, we have:

If we go to a mixed number we have:

Answer:

the factor for this expression is 7
1. Find the unit rate
15 books divided by 5 days = 3 books sold per day.
Since we are looking for how many days it would take the store to sell 21 bucks, we could do 21 (amount of books) divided by 3 (how much books is sold in a day).
Therefore, it will take a week / 7 days to sell 21 books.
Answer:
t>=7
Step-by-step explanation: