Question 761613
Let speed of slower car be x km / hour
Then speed of faster car is x+20 km/hour

At the end of one hour, car 1 would have travelled x km, and car 2 (x+20) km, but in opposite directions. 

Hence the distance between them would be {{{x+x+20 = 2x+20}}} km.

Every hour, the distance between them increases by 2x+20.

At the end of 4 hours the distance would be

4*(2x+20) which is given to be 656. So we get the equation

{{{4*(2x+20) = 656}}} or {{{8*x + 80 = 656}}}

Simplifying

{{{8*x = 656 - 80 = 576}}}

{{{x = 576/8 = 72}}}

So, Car 1 is travelling at 72 Kmph and car2 at 92 Kmph.

:)