Answer
$v_{0x} = 10~m/s$
Work Step by Step
On the graph, we can see that $\Delta x_{bg} = 0$ when $v_s = 10~m/s$
This means that the ball lands at the same location where it was launched.
Thus the sum of the sled's velocity and $v_{0x}$ is zero.
Since the sled's velocity is $-10~m/s$, the value of $v_{0x} = 10~m/s$
