What is number 5 please help

What is the answer to the question 5x+2x

Consider the sequence below. 3 , 1 , 1/3 , 1/9 , select the explicit function which defines the sequence.

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}