we can add two numbers first
[tex]\begin{gathered} 3.95 \\ 4.99 \\ ------ \\ 8.94 \end{gathered}[/tex]now we add the result with the following number
[tex]\begin{gathered} 8.94 \\ 6.05 \\ ------ \\ 14.99 \end{gathered}[/tex]the total of books cost $14.99