The green route is 4.5 miles long.
This is a system of equation problem. You have to set up 2 different equations and then solve them.
You could have:
6g + 5b = 52
12g + 13b = 119
To solve them, you can use graphing, substitution or elimination.
Either way, you will find the blue route is 5 miles and the green route is 4.5 miles.