Answer:
15
Step-by-step explanation:
We find the union of the sets, one for each day.
<em>Monday </em>= {M, O, N, D, A, Y}
<em>Tuesday </em>= {T, U, E, S, D, A, Y}
<em>Wednesday </em>= {W, E, D, N, E, S, D, A, Y} = {W, E, D, N, S, A, Y}
<em>Thursday </em>= {T, H, U, R, S, D, A, Y}
<em>Friday </em>= {F, R, I, D, A, Y}
<em>Saturday </em>= {S, A, T, U, R, D, A, Y} = {S, A, T, U, R, D, Y}
<em>Sunday </em>= {S, U, N, D, A, Y}
<em>Duplicates have been removed in each set.</em>
The union is
<em>Week </em>= <em>Monday </em>∪ <em>Tuesday </em>∪ <em>Wednesday </em>∪ <em>Thursday </em>∪ <em>Friday </em>∪ <em>Saturday </em>∪ <em>Sunday</em>
<em>Week </em>= {M, O, N, D, A, Y} ∪ {T, U, E, S, D, A, Y} ∪ {W, E, D, N, S, A, Y} ∪ {T, H, U, R, S, D, A, Y} ∪ {F, R, I, D, A, Y} ∪ {S, A, T, U, R, D, Y} ∪ {S, U, N, D, A, Y}
<em>Week </em>= {M, O, N, D, A, Y, T, U, E, S, W, H, R, F, I}
<em>(Duplicates are also removed)</em>
The number of elements in Week is <em>n(Week)</em> = 15