The distance traveled by bicycle is 3 *12.5 = 37.5km..
The distance traveled by the car is: (3-0.5) * x = 2.5km..
I think your title is wrong, not 150m, but 150km.
So: 37.5+2.5x= 150.
2.5x = 150-37.5 = 1 12.5
x= 1 12.5/2.5
X=45 km/h