The Solution.
The given function that defined the number of books left unread after reading for t months is
[tex]b(t)=75-5t[/tex]
We shall find b(9), which is, the number of books left unread after reading consistently for 9 months.
[tex]\begin{gathered} \text{Substituting 9 for t in the given function, we have} \\ b(9)=75-5(9) \\ b(9)=75-45 \\ b(9)=30\text{ books} \end{gathered}[/tex]
This means that 30 books were left unread after reading consistently for 9 months.
The correct answer is 30 books unread after reading for 9 months.
