Use the equation
[tex]{v_f}^2-{v_i}^2=2a\Delta x[/tex]
The final velocity [tex]v_f[/tex] is 68 m/s, the acceleration [tex]a[/tex] is 8 m/s^2, and the net displacement [tex]\Delta x[/tex] is 33 m, so you can solve for the initial velocity [tex]v_i[/tex]:
[tex]\left(68\,\dfrac{\mathrm m}{\mathrm s}\right)^2-{v_i}^2=2\left(8\,\dfrac{\mathrm m}{\mathrm s^2}\right)(33\,\mathrm m)[/tex]
[tex]{v_i}^2=4096\,\dfrac{\mathrm m^2}{\mathrm s^2}[/tex]
[tex]v_i=64\,\dfrac{\mathrm m}{\mathrm s}[/tex]
