Help with a few more ​

The radius  of the rim = 18/2  =   9 inches

So.....we need to find the radius of the ball

Circumference  = 2 * pi * radius

30   =  2 * pi  *  radius        divide both sides by *pi

30  / ( 2 * pi)   =  r  = 15/ pi  inches

So  the distance between the rim and the ball  =

[ 9  -  15/pi ] inches  ≈  4.225  inches