Answer:
25 N
Step-by-step explanation:
We are given that three boxes rest side-by-side on a smooth, horizontal floor.



Force applied on 5 kg box=50 N
We have to find the magnitude force exert on the 3 kg box by 5 kg box.
According to given question


When 5 kg box exert force on 3 kg box then equal and opposite force exert on 5 kg box due to 3 kg box and 2 kg box.
Let F be the force exert by 5 kg box on 3 kg box and


Hence, the magnitude force exert on 3 kg box by 5 kg box=25 N