3/4-5/10= in fractions and decimals format

Arestaurant charges $100 to rent its banquet room for an event. it also charges $15 to serve dinner to each guest. write an equation for the total cost of the banquet room in terms of the number of guests. deine your variables. what is the total cost of the banquet room for 20 guests?

Ijust need these 2 questions answered (the second pic is just confirmation i'm not confident in that answer)

Convert (-3,0) to polar form. a. (3,0’) b. (-3,180’) c. (3,180’) d. (3,360’)