predict what would happen if two people with equal mass standing on skateboard pushed against each other

What is a number added in front of a formula in order to balance the equation

How many atoms or molecules are there in a mole of a substance?

Ascientist wants to know how individual lions within a pride interact with each other in their own environment. to do this, the scientist sedates and tags all of the lions within a pride. then, he places several remotely-controlled video cameras near the lions' den and performs an observational field study. he collects continuous video footage over the span of one year, analyzes the video, and then forms conclusions based on his observations.