Hi there!
Recall the equation for momentum:
[tex]\large\boxed{p = mv}\\[/tex]
p = momentum (kgm/s)
m = mass (kg)
v = velocity (m/s)
We can plug in the given values to solve for velocity:
[tex]-450 = 35v\\\\v = \frac{-450}{35} = \boxed{12.86 m/s}[/tex]