If she starts at the fourth level below the ground floor, and wants to get to the fourth floor above ground, then she'll need to take 8 flights of stairs.
You can draw out a number line. Then count the number of steps needed to go from -4 to +4. Or you can subtract the two values and take the absolute value (effectively computing the distance from -4 to +4)
|-4-4| = |-8| = 8
Either way, the final answer is 8
