Given:
The diameter of cloud-water droplet is

The diameter of pinhead is 0.001.
Explanation:
Divide the dimater of cloud-water droplet by dimater of pinhead to determine the times as great is the diameter of a pinhead as the diameter of a cloud-water droplet .

So diameter of a pin-head is 100 times the diameter of water-droplet.
Answer:
see below and attached
Step-by-step explanation:
To solve a system of quadratic equations:
- Equal the equations then rearrange so that it is set to zero.
- Use the quadratic formula to solve.
I have done this (see attached workings) but cannot get any of the solutions you've provided. I have even graphed the two functions, and the points of intersection concur with my workings (see attached graph).
I believe there are 35 backpacks in all. 2 closets have 6 shelves all together. Then 6*5=35.