What must be the normal force acting on a crate as it slides across a horizontal floor if the friction acting on the box is 0.490N and the coefficient of friction is 0.250?

I’m good with pshycology

The purpose of a lab is to do your "expirements" the importance of the topic is so you can now what the story is about and the last one is because no one is me with my question ( what is 3 over 4 x - 9 = 27 maybe you can )