I cannot suggest anything other than the set of real numbers here, but maybe someone else can provide a better answer. As long as you increase or decrease x (which is a real number) then you will get a real number, or the infinite set of real numbers.
An infinite amount seeing as you can have infinite of each number
Answer: y = 0x+3 or y = 3
The slope is 0 and the y intercept is 3. So m = 0 and b = 3.
Plug those into y = mx+b to get y = 0x+3, and that simplifies to y = 3.
This graphs out a horizontal line that passes through the two points (0,3) and (1,3).