The ones i got wrong i need with. show work

I know for 20) its C because you can't have a decimal of a student so you round it to the next whole number and for 23) it's 24 because you do 32*(3/4) 

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.