Below is the question:

Consider the titration of a 20.0 mL sample of 0.105 M HC_{2}H_{3}O_{2} with 0.125 M NaOH. Determine the initial pH levels.

So I know the pH = -log[acid], so I assumed the way to go about this problem is just pH = -log(0.105), which gives me 0.979, which is wrong. The book says the answer is 2.86.

Could someone help explain how I would set up this problem? Thanks!