To find the probability of selecting a slice of mushroom pizza, we need to divide the number of mushroom slices (20) by the total number of slices available (68).
So, the probability of selecting a slice of mushroom pizza can be written as:
P(mushroom) = 20/68
Simplifying this fraction, we get:
P(mushroom) = 5/17
Therefore, the probability of randomly selecting a slice of mushroom pizza is 5/17.