At time t, the ball attains a height y of
y = (30 m/s) sin(53Âș) t - 1/2 g tÂČ
where g = 9.80 m/sÂČ is the magnitude of the acceleration due to gravity.
Solve for t when y = 0:
(30 m/s) sin(53Âș) t - 1/2 g tÂČ = 0
t ((30 m/s) sin(53Âș) - (4.90 m/sÂČ) t ) = 0
t = 0  or  (30 m/s) sin(53Âș) - (4.90 m/sÂČ) t = 0
We ignore the first solution, since that refers to the moment the ball is kicked.
(30 m/s) sin(53Âș) - (4.90 m/sÂČ) t = 0
(30 m/s) sin(53Âș) = (4.90 m/sÂČ) t
t = (30 m/s) sin(53Âș) / (4.90 m/sÂČ)
t â 4.9 s