There is a bag with only red marbles and blue marbles.
the probability of randomly choosing a red marble is
5
12
.
there are 72 marbles in total in the bag and each is equally likely to be chosen.
work out how many red marbles there must be.

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.