Try looking at this and see if it helps http://openstudy.com/updates/580662f4e4b0d88e39fc9a0e
You're given an angle, the side adjacent to the angle, and are looking for the hypotenuse.
Use cosine = adjacent / hypotenuse.
cos(60) = 2√(3) / x
Rearrange the equation to solve for x (multiply both sides by x, then divide both sides by cos(60)).
x = (2√(3)) / (cos(60))
x equates to about 6.928
In this question, each star equal to 4 students. If the people on 85 and 90 take the test again that means their number should be 14+4 people= 18 people.
If they all get 95, then it means we need to add 18 people to the 95 graph. The number of stars would be: 18 people / (4people/stars)= 4.5 stars
If you add the stars graph it will be easier. It should be clear that 85 will have 1 stars and 90 have 3.5 stars. Adding them up will be 1 stars + 3.5 stars= 4.5 stars