Is this for homework or something?
Might as well post all three just in case.
1. An object remains at rest or in motion unless acted upon by an external force. (The concept of inertia).
2. In the presence of a net force, an object experiences acceleration directly proportional to the net force and inversely proportional to the mass of the object. (F = m x a)
3. For every action, there is an equal and opposite reaction.
Edit: Neo beat me to it. Mass is usually in kilograms.