The top 4 firms have (23 +22 +18 +12)% = 75% of the market.
The 4-firm concentration ratio is 0.75 or 75%.
Answer:
68/5 is already in the simplest form. It can be written as 13.6 in decimal form (rounded to 6 decimal places)
To find the slope, you can use the formula:
. Start at where the graph intersects at the y-axis, which is -4. So, it rises up 2 units and goes left 3 units, which makes the slope
.
To find the y-intercept, you would start at where the graph intersects at the y-axis, which is -4 and this would be the y-intercept.
To find the equation, you can use the formula: y = mx + b. m is slope and b is the y-intercept. Plug the slope and y-intercept you found earlier. Thus, your final answer should be: 
Please reach out to me if you are still confused. Hope this helps :)