Where is it? In order to help you I need to see what the problem is.
It is in between
And
There for it is in between 5 and 6
Additionally, it is closer to root 25, meaning that it is closer to 5
Rounded to the nearest hundredth is
5.29
X = 32 because 100 / 4 is 25, which would make the numerator for x 32
The top 4 firms have (23 +22 +18 +12)% = 75% of the market.
The 4-firm concentration ratio is 0.75 or 75%.