What values of n makes the equation 4(0.5n-3)=n-0.25(12-8n) true?

Quick translate "x is 12 units from 20" into an equation. what are the values of x being described? if you can answer any of my other questions that'd be great too

What are the soultion(s) to the quadratic equation 40- x^2=0

3. a sum of $2700 is to be given in the form of 63 prizes. if the prize is of either $100 or $25, find the number of prizes of each type.