A) You're just plugging in an "x" into the given equation here, and you need 8. I'd go with numbers that divide into whole integers by 8 (e.g. -4, -2, 2, 4), write down the x, then "y" after plugging into the equation.
B) Plot the coordinates you got from the first problem.
C) Any linear function has the domain of all real numbers, meaning that you can plug in any "x" and it'll work. What if you have a rational (something in the denominator) function though and x is in the denominator? Well, if we plug in any number and divide by 8, it works, BESIDES 0. You cannot divide by zero, and we call this "undefined" in math. There is no definitive nor quantitative answer, it is simply "undefined" because you can't divide something by 0
