We have a situation expressed with the following equation
[tex]L(d)=58+d[/tex]
where L is the miles after a number d of days and d is the number of days
we must find the miles after 31 days of construction, i.e. we replace the value d = 31
[tex]\begin{gathered} L(31)=58+31 \\ L(31)=89 \end{gathered}[/tex]
In conclusion, the answer is 89 miles
