Which equation is a function of x? x = 5

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

Celeste wants to have her hair cut and permed and also go to lunch. she knows she will need $50. the perm cost twice as much as her haircut and she needs $5 for lunch. how much does the perm cost?

What is always true when two whole numbers are subtracted?