Question

A 10 kg backpack is on the floor. Someone gently pulls on it, upwards with a 15 N force. What is the normal force acting on the backpack?

Answer 1

maybe 25gs of force because 10+15=25
  

Answer 2

If backpack was simply at rest then normal force would be 100N( g=10m/s^2). It's is being pulled gently in upward direction. So Normal force will be. N= mg - 15 = 10x10 - 15 = 85N. I took g=10m/s^2 for simplification. Hope it helps.