Answer: 1
Step-by-step explanation:
[tex]f(8+h)=8+h+10=18+h\\\\f(8)=8+10=18[/tex]
So, the average rate of change is:
[tex]\frac{(18+h)-18}{(8+h)-8}=\frac{h}{h}=\boxed{1}[/tex]
The question is wrong, the expression will not be in terms of h since it is a linear function.