The answer to the first part is 3 1/2 and the answer to the second question is 2/7
For something to be a function, each input (x value) can only have ONE output (y value)
If an input has multiple outputs, it is not a function.
so the last graph represents a function (parabola going down)
The commutatice property for addition says a+b=b+a
If it was for subtraction, then it would be a-b=b-a
Take a=7 and b=5
7-5 is not equal to 5-7
2 is not equal to -2
So subtraction is not commutative for whole numbers.
Hope this helps :)
