They got 90 but i'm getting 30 anyone who can ?

the answer to your question is 90

Ignore the mass of the car.  It doesn't figure into this problem at all.

-- The car's speed is zero at the beginning, and 30 m/s after 6 sec.

-- The car's AVERAGE speed during the 6 seconds is 15 m/s.

-- Moving at an average speed of 15 m/s for 6 seconds, the car moves

(15 m/s) x (6 sec)  =  90 meters .

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

it is called kinetic energy