Question 321994
To evaluate a function, we insert a given x value, a number in the domain, and see what number we get, which is a number in a range.  

SAMPLE:

f(x) = x + 2

Pick a number for x.  Any number will do.

Say, x = 3.

f(3) = 3 + 2

f(3) = 5

Here, 3 is the number in the domain of the function and 5 is the range of the function.

Understand?