A boy on a 1.9 kg skateboard initially at rest

Question

tosses a(n) 8.0 kg jug of water in the forward
direction.
If the jug has a speed of 2.7 m/s relative to
the ground and the boy and skateboard move
in the opposite direction at 0.65 m/s, find the
boy’s mass.
Answer in units of kg

Answer 1

reaction=action
(1.8+M).65=8*2.7
solve for M