Question

if A and B are disjoint sets,how can you find n(AuB)

Answer 1

obviously if A and B are disjoint set so their is no common element between A and B so 
if there is no common element between A and B then n(AυB)=n(A)+n(B)
i.e no of element of set A plus the no of element of set B
i hope you understand  have attached a image for you to upgrade your concept of set

Answer 2

Answer:

Step-by-step explanation:

obviously if A and B are disjoint set so their is no common element between A and B so 

if there is no common element between A and B then n(AυB)=n(A)+n(B)

i.e no of element of set A plus the no of element of set B

i hope you understand  have attached a image for you to upgrade your concept of set

Ok dude