twice one number added to three times another gives 21 find the numbers if the difference between them is 3

Guests at an amusement park must be at least 54 inches tall to be able to ride the roller coaster. which graph represents the set of heights that satisfy this requirement?

Given f(x)= 9x+1 and g(x)=x^3, choose the expression (f*g)(x)

Astuntman jumping off a 20-m-high building is modeled by the equation h=20-5t^2, where t is the same in seconds. a high-speed camera is ready to film him between 15m and 10m above the ground. for which interval of time should the camera film him?