There are 7 students in a class: 5 boys and 2 girls. • If the teacher picks a group of 4 at random, what is the probability that everyone in the group is a boy

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.