AD and CG are diameters of circle B. Identify each arc as a major arc, minor arc, or semicircle, Arc ACF

After t seconds, a ball tossed in the air from the ground level reaches a height of h feet given by the equation h = 144t-16t^2. after how many seconds will the ball hit the ground before rebounding?

9/10 divide by -3/15 as a mixed number

We just started the introduction into circles and i have no idea how to do this.