How many elements are i the set { whole numbers between 3 and 15}

Can someone answer this question for me

Charlie is at an amusement park that has 18 different rides. each ride costs $1.75. the function c(r) = 1.75r represents the total amount of money that charlie will spend if he goes on r rides, but he never goes on the same one more than once. what domain and range are reasonable for the function?

Solve for the equation x. 2x + 22 = 4(x + 3)