A water pipe is turned on and the water pipe goes backward what one of Newton's laws is this an example of?

Newton's third law. " To every action there is always opposite and equal reaction"

This is Newtons' third law. According to this law when an object exerts a force on the second object, the second object exerts a force on the first object which is in the same magnitude. In your question, water experiences force as forward direction while pipe experiences the same amount of force in opposite direction. In IB and A-Level physics, this law is used to explain the reason for the conservation of momentum in water and pipe systems.

Newtons Third Law. Pipe forces water forwards, so water forces pipe backwards with equal force. Not unlike jet engine-engine forces air backwards so air forces engine forwards with equal force.

Newton's Third Law : To every action, there is an equal but opposite reaction.

This is an example of Newton's 3rd law of action and reaction.

Action: The pipe is spewing water forward.

Reaction: The water is pushing back against the pipe, making it go backwards.

This is an example of Newton's first law.