This question tests the basic concept of evaluating a function at given points. The function f(x) = 2x - 5 is a linear function of the form f(x) = mx + c (as mentioned in the Remark in Example 18). To find the value of the function at any point, we simply substitute the given value of x into the function expression. This is demonstrated in Example 18 where f(0), f(1), f(-1) etc. are calculated by direct substitution.