Explanation:
Let's start by representing the change in depth of the snowdrift as negative, since it decreased by 8 inches over the first four days.
Change from Monday to Thursday = -8 inches
Now we need to find the change in depth from Thursday to Friday. We're told that the depth changed by half as much as it did from Monday to Thursday. So we can start by finding half of -8 inches:
Half of -8 inches = (-8)/2 = -4 inches
Therefore, the change in depth from Thursday to Friday is -4 inches.
To summarize:
Change from Monday to Thursday = -8 inches
Change from Thursday to Friday = -4 inches