Find the ratio of a 1 1/2 diameter to a 4 9/10

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?

What is the percentile for data value 6 in the following data set? 4 13 8 6 4 4 13 6 4 13 2 13 15 5 9 4 12 8 6 13 40 25 35 62