Transformations of Functions - Algebra 2

i don’t understand this :(

Ahome improvement store rents it’s delivery truck for $19 for the first 75 minutes and $4.75 for each additional 1/4 hour. if a customer rented the truck at 11: 10 am and returned the truck at 1: 40 pm the same day, what would his rental cost be?

If f(x)=2x-6 and g(x)=3x+9, find (f-g)(x)

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?