Jerry was playing a video game. it took him 10 lives to beat the 2nd world, 5 times as many as it took him to beat the 1st world. how many lives did he use to the 1st world?

The area (a) of a circle with a radius of r is given by the formula and its diameter (d) is given by d=2r. arrange the equations in the correct sequence to rewrite the formula for diameter in terms of the area of the circle.

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?