Answer:
\(v_0=7.938\frac{m}{s}\)
Explanation:
This is uniformly accelerated motion, that is to say a motion with constant acceleration, we can use the kinematic equations, especifically the which one that relate the change in speed to acceleration and time:
\(v_f-v_0=at\)
So, Rewriting for initial speed:
\(v_0=v_f-at\\v_0=9.81\frac{m}{s}-(6.24\frac{m}{s^2})0.3s\\v_0=9.81\frac{m}{s}-1.872\frac{m}{s}\\v_0=7.938\frac{m}{s}\)