I need an answer ASAP

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

Amerchant has coffee worth $60 a pound that she wishes to mix with 50 pounds of coffee worth $90 a pound to get a mixture that she will sell for $70 a pound. how many pounds of the & 60 coffee should be used?

Brent wants to know what is 5 x 1/2