Need , how do you answer this question

The answer is the third option, .

They're asking you to find the union of the two sets of numbers, set  and set .

Set  contains all numbers less than . 
Set  contains all numbers less than or equal to .

The union of both sets will include the numbers in both of the sets altogether, or . Since any number less than  (from set ) is already contained in all numbers less than  (from set ), you can just write your final answer as set , which is .

Hope that makes sense!

Iwould say they are complementary because that’s the division of a 90 degree angle and it’s split between the middle of them