The equation of momentum is:
[tex]p=mv[/tex]
Where p is the momentum, m is the mass and v is the velocity. In this case the mass of the person and the mass of the bike so:
[tex]m_{total}=mass_{person}+mass_{bike}=37kg+18kg=55kg[/tex]
And the velocity of the person riding the bike is 1.2 m/s and so:
[tex]p=(55kg)(1.2m/s)=66 \frac{kgm}{s}[/tex]
