Exam review question (acceleration)

[Axson]

Homework Statement

A force of 1 N pushing on a mass m1 results in an acceleration of 1.0 m/s2. The same force acting on mass m2 results in an acceleration of 3.00 m/s2. What is the acceleration a3 for the same force pushing the combination of m1 and m2?

Homework Equations

well I know that acceleration = force/mass lol

The Attempt at a Solution

this is a example problem for my first test tomorrow morning.. honestly I don't have a clue how to solve this problem and a good explanation would be very helpful.

two other problems from the exam review

ACCELERATIONS for SAME FORCE on DIFFERENT MASSES

A force F acting on a mass m1 results in an acceleration a.
The same force F acting on mass m2 results in an acceleration 0.20 a.
What is the acceleration anew for F pushing the combination of m1 and m2?

A force F of 3 N acting on a mass m1 results in an acceleration of 1 m/s2.
The same force F acting on mass m2 results in an acceleration of 0.20 m/s2.
What is the acceleration a3 for F pushing the combination of m1 and m2?

 

[Winzer]

Well we know that:
$$\vec{F}=m\vec{a}$$
What is m in this situation?
What is the total mass?

 

[Axson]

do you combine the masses? i mean really i don't have a clue how to solve this problem