Answer:

U={1,2,3,4,5,6,7,8,9}

Step-by-step explanation:

A universal set is a set of all elements trust me I'm a college student now

Answer:

U={1,2,3,4,5,6,7}

Step-by-step explanation:

set of A,B,and C:just mix them

so that is the final answer

I hope it helps☺️