Answer:
Yes, the game is fair.
Step-by-step explanation:
In order to check that the game is fair we will see that the total expectation is zero.
i.e. Bob will hover around the same place.
There are total 20 tiles in a container.
( Since 5 red tile+11 green tile + 4 blue tile=20 tiles)
The probability of choosing a red tile is:
Number of red tile/total number of tiles
= 5/20
Also, the probability of choosing a green tile is:
Number of green tile/Total number of tiles
= 11/20
Also, the probability of choosing a blue tile is:
Number of blue tiles/ Total number of tiles
= 4/20
Let E denote the expectation of an event.
Hence,

Since when a red tile is drawn Bob moves 12 spaces forward.

Similarly

Since when a green tile is drawn Bob remains at the same place.

and

Since when a blue tile is drawn Bob moves 15 spaces backward

Hence, total expectation is:

This means that he will around the same place.
Hence, the game is fair.