Help me please. What does x equal

How many different ways can you make change for $.50 using only nickels,dimes, and quarters?

If c(x) = 4x – 2 and d(x) = x2 + 5x, what is (cxd)(x)

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?