Part A:
When Yolanda began driving, the number of hours she has been driving is 0. Thus, we substitute x = 0 to the given equation and we get
Therefore, Yolanda's distance from Miami when she began her drive is 375 miles.
Part B:
In the equation, x represents the number of hours she has been driving, and this is multiplied by -55, this implies that for each hour she drives it changes by -55 miles.