Can someone check my answers for two and help me with the third?

Question

1) A mass m at the end of a spring of spring constant k is undergoing simple harmonic oscillations with amplitude A.

Part (a) At what positive value of displacement x in terms of A is the potential energy 1/9 of the total mechanical energy?
x= A/3

Part (b) What fraction of the total mechanical energy is kinetic if the displacement is 1/2 the amplitude?
KE fraction= (3/4)

Part (c) By what factor does the maximum kinetic energy change if the amplitude is increased by a factor of 3?
KE'max / KEmax = ?

Answer 1

Part (c)9

Answer 2

The Answer is 9.

Answer 3

a is A/3

Answer 4

Can someone explain what formula is being used to come up with A?

Answer 5

A and B are correct and C is 9