To find the probability of randomly selecting an employee who eats breakfast or lunch at the office, we can use the formula P(A or B) = P(A) + P(B) - P(A and B).
P(Breakfast) = 20/80 = 1/4
P(Lunch) = 50/80 = 5/8
P(Breakfast and Lunch) = 10/80 = 1/8
P(Breakfast or Lunch) = P(Breakfast) + P(Lunch) - P(Breakfast and Lunch)
= 1/4 + 5/8 - 1/8
= 2/8 + 5/8 - 1/8
= 6/8
= 3/4
Therefore, the probability of randomly selecting an employee who eats breakfast or lunch at the office is 3/4 or 75%.