SOLUTION
The cost per student =$5
Then let the total cost be C(n) and n be the number of students
Then required function is
[tex]C(n)=5n+30[/tex]if the total number of student is 20, n=20
The total cost is
[tex]\begin{gathered} C(n)=5n+30 \\ C(n)=5(20)+30=100+30=130 \end{gathered}[/tex]Then the total cost is $130
If the total number of student is 25, then n=25
The total cost becomes
[tex]\begin{gathered} C(n)=5n+30 \\ C(n)=5(25)+30=125+30=155 \end{gathered}[/tex]