(a) The rock has a weight w according to
w = m g
where m is its mass and g = 9.80 m/s² is the magnitude of the acceleration due to gravity. So
w = (20.0 kg) (9.80 m/s²) = 196 N
(b) Charmander kicks the rock with an upward force (magnitude f ) that overcomes the weight of the rock, and the net force on it is 230 N. This means
f - w = 230 N
f - 196 N = 230 N
f = 426 N
(c) I think the question is supposed to say, "What is the acceleration of the rock," and not asking about Charmander's acceleration. By Newton's second law, the net force on the rock is equal to its mass times its acceleration:
230 N = (20.0 kg) a
a = (230 N) / (20.0 kg)
a = 11.5 m/s²