If the water was still, the canoe would cross with a constant velocity of 1.2 m/s. However, the river has a velocity and thus pulls the canoe in its direction of flow resulting to a higher velocity of 3.2 m/s.
These vectors forms a right-angle triangle with 3.2 m/s as the hypotenuse and 1.2 m/s as the adjacent length. Resolving for the opposite site which represents the river flow velocity, results to:
River speed = Sqrt (3.2^2-1.2^2) = 2.995 m/s
To nearest tenth, river speed = 3 m/s
