P = {a, b, i, l, o, p, r, t, y} <-- This set contains all unique elements (letters) in the word "probability"
S = {a, c, i, s, t} <-- This set contains all unique elements (letters) in the word "statistics"
P ∩ S = {a, i, t} <-- This set contains only elements (letters) that are contained in BOTH the words "probability" and "statistics"
(M ∪ P ∪ S)' = {a, b, c, e, h, i, l, m, o, p, r, s, t, y}' = {d, f, g, j, k, n, q, u, v, w, x, z} <-- This set contains only elements (letters) that are NOT found in either the words "mathematics", "probability", or "statistics"
Hope the answers and explanations helped!