Optimize calc() usage in scss files

[AMoo-Miki]

Moving from node-sass to sass-embedded, all the divisions had to be converted to calc(). There is an opportunity to make the code look nicer by moving some of the math around these calc() calls inside it. However, these changes should be mindful of the units of the variables since mixed %, px, and *em will need to be calculated at runtime.

[ShatilKhan]

@AMoo-Miki @joshuarrrr
If this issue is open, I'd like to take this one