Solution:      

Weight of the car = w = 12kN = $12\times 1000$ N = 12000 N
Speed of the car = v= 20 $ms^{-1}$ 
Kinetic energy = K.E. = ?

K.E. = $\frac{1}{2} m v ^{2}$
W = mg or m = $\frac{w}{g}$
m = $\frac{12000}{10}$ = 1200 kg

Thus, K.E. = $\frac{1}{2}\times 1200 \times (20)^{2}$
= $600 \times 400$ = 240000 J
K.E. = 240 kJ