The associative property allows you to change the <em>grouping</em> of addends or factors without changing the value of the expression.
Answer:
Step-by-step explanation:
∩
is asking for the intersection of sets
and
, or simply, which numbers can be found in both sets.
The numbers shared between the two sets are
.
Next, we need to union this result with the set
, or simply, combine the numbers in both sets together.
This would result in 
40 Why? 80%x X=50 or 80/100x X=50
the formula for volume of a prism is base x height