Kinetic energy is the energy that an object has due to the fact that it is moving. The kinetic energy of a body with mass m moving with a velocity v is give by (1/2)*m*v^2
The car B is travelling twice as fast as car A and the mass of car A is three times that of car B. If we denote the mass of car A as M and the velocity of car A as V, the mass of car B is M/3 and its velocity is 2*V
The kinetic energy of car A is (1/2)*M*V^2.
The kinetic energy of car B is (1/2)*(M/3)*(2*V)^2 = (1/2)*(M/3)*(4*V^2)
We see that the kinetic energy of car B is (4/3) that or car A. This implies that car B has a greater kinetic energy of the two cars.