The unemployment rate is calculated as the number of eligible persons that are unemployed.
So we would need to remove all the population that is out of the workforce (those who are not eligible to work like the elderly or children).
We know that the total population is 8,000,000 and we can account for 5,500,000 of them so the eligible population of workers is 5,500,000.
If 500,000 of them are unemployed, the rate would be 500,000/5,500,00 or 9%
To find the share of the labor force, take the total eligible (5,500,000) divided by the total population (8,000,000)
5,500,000/8,000,000 = 68.8% of the total population is in the labor force.