what is the answer to this

What’s the scientific notation for the number 6,840,000,000

Astudent carefully transfers 30 g of water and 30 g of alcohol in a glass tube, forming two layers and filling the tube completely. after sealing the tube, the student mixes the solutions, and notices a bubble that forms in the tube. what is the mass of the contents in the glass tube after mixing?

This drawing shows a human body system. what is the primary function of this body system?