A good answer might be:

4095

Hopefully you did something clever: you realized that the represented number is 2N - 1 which must be an odd number. ( 2N means 2 × 2 × 2 ... × 2 it must be even. So 2N - 1 must be odd. )

So you picked the only odd number in the list. Or else you ignored the question.

Base 16 Representation

Rules for Positional Notation.

  1. The base B is (usually) a positive integer.
  2. There are B "digits" representing zero up to (B minus one).
  3. Positions correspond to integer powers of B, starting with power zero, and increasing right to left.
  4. The digit placed at a position shows how many times that power of B is included in the number.

Rule 1 says any positive integer can be used as a base. Let's use sixteen as a base. Rule 2 says we need sixteen symbols to use as digits. Here is the usual choice:

0123456789ABCDEF
zeroonetwothreefourfivesixseveneightnineteneleventwelvethirteenforteenfifteen

Since there are only ten of the usual digits, letters are used for the remaining six hex "digits".

Base sixteen representation is called the Hexadecimal system, sometimes further shortened to Hex.

QUESTION 7:

Fill in the blanks with BASE SIXTEEN digits 

31A (base sixteen)   = 

   ____ × sixteen2 +____ × sixteen1 +  ____ × sixteen0