I'm unsure how to do this question,, could someone help?

Bring the fraction a/a-4 to a denominator of 16-a^2

Let u = {q, r, s, t, u, v, w, x, y, z} a = {q, s, u, w, y} b = {q, s, y, z} c = {v, w, x, y, z}. list the elements in the set. a ∩ (b ∪ c)a) {q, s, w, y}b) {q, y, z}c) {q, s, u, w, y, z}d) {q, r, w, y, z}

Last week , donnell practiced the piano 3 hours longer than marcus . together, marcus and donnell practiced the piano 11 hours . for how many hours did each young man practiced the piano