By this method, the probability of successes in trials, where the probability of success is and the probability of failure is is given by:
let "absent" be our "success" here, since that is what we are looking for. then the probability of success is p = 0.02 and the probability of failure is q = 1 - 0.02 = 0.98. we have n = 50 trials.
now, we want the probability that no more than 2 are absent, that means, 2 or less would be absent. that is, the probability that 2 people are absent, OR 1 person is absent, OR no one is absent. thus you want:
i leave the computations to you