Question

if A and B are two sets such that AcB then what is AuB? ​

Answer 1

$\huge \text{\mathbb {\underline {ANSWER}}}$

$A \cup B = B$

$\huge \text{\mathbb {\underline {EXPLANATION}}}$

If A and B are two sets where

$A \subset B$ then all the elements of A∈B

Therefore,

$A \cup B = B$

This can be explained easily by Venn diagrams

The adjoining Venn diagram explains it