If a company has 5 employees with annual salaries of 90000 60000 70000 90000 and 20000 respectively what is the mean annual salary at the company?

The "mean" salary is the average, i.e. the sume of all salaries divided by the number of salaries - thus

Mean salary = (90,000+60,000+70,000+90,000+20,000)/5 = 66,000

On the other hand, the MEDIAN salary would be 70,000 since half of the salaries are above that value and half below it.