Step 1
From the question;
[tex]\begin{gathered} Bobby\text{ reads 20 books in 2 months} \\ \end{gathered}[/tex]We are required to find how many months it will take him to read 90 books
Step 2
We will use the ratio below to solve the problem.
[tex]\begin{gathered} \frac{20\text{ books}}{90\text{ books}}=\frac{2months}{x} \\ x=months\text{ to read 90books} \\ x=\frac{90\times2}{20} \\ x=9\text{ months} \end{gathered}[/tex]Answer; It will take Bobby 9months to read 90 booj
[tex]9\text{ months}[/tex]