1/2 of 20 is 20/2 which is 10.
All you really need to do here is to divide 20 by 2 to get 10.
If it's -4+8, -4 is 4 less than 0. 8 is 8 more than 0, also 4+4. so -4+4 would be zero, then there's 4 more and 0+4 is 4
ANSWER
The relation is not a function.
EXPLANATION
The relation is not a function because we have an x-coordinate mapping on to more than one y-coordinate.
This occurs at x=1.
The ordered pairs (1,1) and (1,3) disqualify the relation from being a function.
Hence the relation is not a function.
Answer in 2.161 tell me if i made a mistake.