Given:
Total students, T=432.
The number of students to which the books were given, N=398.
Let x be the number of students still in need of book.
So, the expression for the total students T is,
![\begin{gathered} T=x+N \\ 432=x+398 \\ x+398=432 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/jb0yrzvotg9pjgxmu7hmzkjys5f9rexomk.png)
Solving the above equation for x, we get
![\begin{gathered} x=432-398 \\ x=34 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/2kkhbptwp4j0bdg4ix5iw84vf0scsauwi8.png)
Hence, x+398=432 and x=34 helps to find the number of students still in need of book.