简单呀；
18km/h=5m/s;
--> a=0,4
so V=V0+at;
t=10s;
then v=5-0.4*10;
V= 1m/s;
in 15s the car have been stopped at 5/0.4=12.5s,so last 2.5s the car is keeping static;
then all the distance the car travelled was:
1/2 × a × t^2 = 0.5* 0.4 * 12.5^2 = 31.25m;
or (0+5)/2 * 12.5 = 31.25m;
That's so easy,so keeping thinking by yourself;