The sum of twice a number and half the number is 10

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

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?

The letters g e o r g i a are placed in a bag . if you picked a card and knew it was a vowel , what is the probability that it is an a ?