Answer:
The total length of the road after the crew has worked 31 days is 183 miles.
Explanation:
As given
A construction crew is lengthening a road. 
The road started with a length of 59 miles, and the crew is adding 4 miles to the road each day. 
let L represent the total length of the road (in miles).
let D represent the number of days the crew has worked. 
Than the equation becomes
L = 59 + 4D
Now find out the total length of the road after the crew has worked 31 days.
D = 31 days 
Put in the equation 
L = 59 + 4 × 31
 = 59 + 124
 L = 183 miles 
Therefore the total length of the road after the crew has worked 31 days is 183 miles.