Answer:
Route A is 0.75 km longer than route B.
Step-by-step explanation:
Length of route A is 1.5 times the length of route B.
a = 1.5b

--------(1)
Here, a = Length of route A
b = Length of route B
Length of route A is
of route C.
a = 
------(2)
Here, c = Length of route C
Length of route C = 3 km
Length of route A =
[From equation (2)]
= 2.25 km
Length of route B =
[From equation (1)]
= 1.5 km
Difference in route A and route B = 2.25 - 1.5
= 0.75 km
Therefore, route A is 0.75 km longer than route B.