Answer
(a) mass = 24.0 kg
(b) The weight is 235 N on Earth and 288 N on the other planet.
Work Step by Step
(a) The mass of the ball is always 24.0 kg.
(b) On Earth:
$weight = (24.0 ~kg)(9.80 ~m/s^2)$
$weight = 235 ~N$
On the other planet:
$weight = (24.0 ~kg)(12.0 ~m/s^2)$
$weight = 288 ~N$