Domain is the x-intercept(first number) for example if I were told to find the domain in (1,3)(4,7)(8,9) the domain would be 1,4, and 8 because they're the x-factors and then plotting a point, the x-factors come first.
Range is the y-factors(second number) and given an example above, the ranges would be 3,7, and 9 because when plotting, they are the second number.
You can tell if it is a function or not if the X-factors repeat. For example, the first one is NOT a function because the 2 repeats for the x-factor. Number 2 IS a function because the x-factor doesn't repeat.
Sorry if this doesn't make sense, that's the best way I can explain!