Using the domain values {-1, 0, 4}, find the range values for relation f(x)=3x-8.

So, this is a line, right? Then, the range, which is basically the min and max values of the values of f(x) ('vertical axis') can be found by substituting the extremes of the domain ('x axis'). There will be no ups and downs since it's a line:

Range = {3*(-1)-8, 3*4-8} = {-11,4}