To determine the initial length, we have to evaluate the given equation at x=0. Evaluating the equation, we get:
![y=3\cdot0+59.](https://img.qammunity.org/2023/formulas/mathematics/college/kwbd7zt5r6yx8waxs8ojy0zohq51vnyhha.png)
Therefore, the initial length of the road was 59 miles.
Now, notice that the given equation is a linear equation in slope-intercept form y=mx+b, where b is the slope, recall that the slope of a line represents the change of y compared to the change in x, in this case, miles per day.
Therefore, the change per day in the road's length is 3 miles.
Answer:
a) 59 miles.
b) 3 miles.