A quality inspector picks a sample of 25 tubes at random from a very large shipment of tubes known to contain 10% defective tubes. What is the probability that exactly 2 of the tubes picked are defective?

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.