Make direction of blue car positive (therefore direction of red car is negative).Momentum = mass x velocitymomentum of blue = 0.9 (remember to convert grams to kilograms) x 0.6 = 0.54 kgm/smomentum of red = 1.6 x -0.2 = -0.32 kgm/s (remember momentum uses velocity and the red car's velocity is negative because velocity is a vector and we have defined the opposite direction positive at the start).therefore total momentum before = 0.54 + (- 0.32) = 0.22 kgm/sMomentum before = momentum after = 0.22total mass = 0.9 + 1.6 = 2.5kgVelocity = momentum/ mass (rearranging earlier equation) therefore the new velocity = 0.22/2.5 = 0.088 m/s (travelling in the direction of the blue car)