The probability that he will attend Math class = 1 - 0.24 = 0.76. The probability that he will attend Biology class = 1 - 0.11 = 0.89. The probability that he will attend both classes = 0.69 ( ! given ! ) The probability that he will attend at least one of the two classes = 0.76 + 0.89 - 0.69 = 0.96. (*) The probability that he will skip both classes is the complement to (*) 1 - 0.96 = 0.04. Answer. The probability under the question is 0.04.