Need with this inequality asap . it's #2

Gregory draws a scale drawing of his room. the scale that he uses is 1 cm : 4 ft. on his drawing, the room is 3 centimeters long. which equation can be used to find the actual length of gregory's room?

Icould really use some with this question.

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