Greatest common factor of 21, 35, 49

What is the radius of a circle with an area of 78.5 cubic inches? use 3.14 for pie

Can someone, me with this.i really need with this

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?