Question 160122
Is this a function:

x + y = 12


a. yes
b. no
c. it depends
d. none of the above

A function is a well-behaved relation.

Based on this definition, then it is a function.

There is a relationship between x and y.  Together they add up to 12.

We can also replace x with different numbers and then subtract those numbers from 12 to find different y values and vice-versa.

So, yes, it is a function.