Answer:
The visitor attended no special exhibits and so paid a total of $10 just to get in.
An equation to represent the cost of admission could look like this:
f(x) is the total cost.
x is the number of special exhibits attended.
f(x) = 2x + 10
If I see no special exhibits on my visit,
x = 0, then
f(0) = 2•0 + 10
f(0) = 10
I only pay $10.