Given:
[tex]c(x)=800+20x[/tex](a)
Value of function then x is 10.
so:
[tex]\begin{gathered} c(x)=800+20x \\ x=10 \end{gathered}[/tex][tex]\begin{gathered} c(10)=800+20(10) \\ c(10)=800+200 \\ c(10)=1000 \end{gathered}[/tex](b)
Function at x = 50 then:
[tex]\begin{gathered} c(x)=800+20x \\ x=50 \\ c(50)=800+20(50) \\ c(50)=800+1000 \\ c(50)=1800 \end{gathered}[/tex](c)
At x = 200.
[tex]\begin{gathered} c(x)=800+20x \\ x=200 \\ c(200)=800+20(200) \\ c(200)=800+4000 \\ c(200)=4800 \end{gathered}[/tex]