Acanoeist at a lake throws a 0.145 kg ball at 20.0 m/s to a friend in a different canoe. each canoe with its contents has a mass of 120 kg, and is at rest initially. how fast is the first canoe moving after the pitch assuming there is no water friction?

The problem above may be solved through the concept of conservation of momentum such that, 
                                      m₁v₁ = m₂v₂
Substituting the given from the problem above,
                                  (0.145 kg)(20 m/s) = (0.145 kg + 120 kg)(v₂)
                                     v₂ = 0.024 m/s
Therefore, the answer is 0.024 m/s. 

The first answer is correct

Did u want to find the value of x?