To evaluate: The length of abandoned road used to make the new road and whether the cost to make new road directly to connect the town is less than $6.8 million.
The length of abandoned road used to make the new road is 16 mi and the cost to make new road directly to connect the town is not less than $6.8 million.
Given:
The town Foxton lies 10 mi north of and abandoned eastwest road. The distance between the point on the abandoned road closest to Foxton is 40 mi from Grimley.
The cost for restore the old road is $100,000 and cost to make new road is $200,000.
The total money spend to make the road is $6.8 million.
The total money spend to make the road is $6.8 million.
Cost for new road is $200,000.
Calculation:
Let the length of abandoned road used to make the new road be x and the remaining part of road be
Length of new road is,
Tabulate the given information into the language of algebra.
In words  In algebra 
Length of abandoned road use to make new road  x 
Remaining part of abandoned road 

Length of new road 

Old cost road 

New cost road 

Model the equation for the above information.
Simplify the above equation for x.
Take square of both sides of above equation.
Factor the above equation.
Thus, length of abandoned road used to make the new road is 16 mi.
The length of new road connecting two towns directly is,
The length of new road connecting two towns directly is 41.231 mi.
The cost for new road is,
Thus, the cost to make new road directly to connect the town is not less than $6.8 million.