Answer:
Assuming that the masses of the cars are the same
9 times
Step-by-step explanation:
Kinetic energy can be computed using the formula:

Where:
KE = Kinetic energy
m = mass
v = velocity
As you can see in your problem, the velocity of the the first car mentioned is 3 times faster.
Looking at the the formula, velocity is raised to two (2). So if we put it in terms of equations this is how it will look:
Let v = velocity of the slower car
Car 1: velocity = (3v)



The increase is by a factor of 9.