ANSWER

Step-by-step explanation
The maximum height of the ball occurs when the final velocity of the ball is 0 m/s.
Since the ball is thrown upwards, its acceleration is the acceleration due to gravity.
To find the maximum height reached by the ball, apply one of Newton's equations of motion:

where s = vertical distance traveled
v = final velocity
u = initial velocity
Note: -g is used instead of a since the acceleration, a, is the acceleration due to gravity in the negative(upward) direction.
Therefore, solving for s in the equation above:

That is the maximum height that the ball reached.