ok so this is just the first one but i think you use a variable for what you are trying to find out, and well call this x and then u subtract the variable from the product of the rate and the amount, and once you have it, you multiply it but its own conjugate so then u use the binomial that you get to create a function, and you can graph it if you want, and u can use the apothem (the formula involves cos, so you might need a calculator) of the polygon created on your graph to find the domain, which you will then get the 4th root of, which is your answer. anyway, i believe this is what it is, but i may be wrong. hope this helps!
