Answer: 37 km
Step-by-step explanation:
Given
The total length of the three roads is 245 km
Suppose the length of PQ is [tex]x\ km[/tex]
According to question
The Length of PR is [tex]x+15[/tex]
The length of QR is [tex]3(x+15)[/tex]
The Sum of PQ, PR, and QR is
[tex]\Rightarrow x+x+15+3(x+15)=245\\\Rightarrow 5x+60=245\\\Rightarrow 5x=185\\\Rightarrow x=37 km[/tex]
length of PQ=37 km