The domain are the x values.
The problem is saying the x value is all numbers between 4 and 8
Replace x in the equation with 4 and 8 and solve to find the range for the y values:
y =4(4) -1 = 16-1 = 15
y = 4(8) - 1 = 32-1 = 31
So Y would be between 15 and 31.
The first answer is the correct one.
