The equation is given in the question.
[tex]x+2y=8[/tex]
To determine the y in terms of x ,
[tex]y=\frac{8-x}{2}=4-\frac{x}{2}[/tex]
Replace y with f(x),
[tex]f(x)=4-\frac{x}{2}[/tex]
The value of f(5) is
[tex]f(5)=4-\frac{5}{2}=\frac{3}{2}[/tex]
The value of f(5) is 3/2.
