Question 1044481
The way I do this is that the cars are going in opposite directions and after 3 hours they are 270 miles apart.
270 miles/3 hours=90 miles/ hour is the separation speed and that is the combined speed of both cars.  Therefore,
car a+car b=90
but car a -20=car b, which means that car b is 20 mph slower than car a
substitute into the first equation.
car a+car a-20=90
2 car a=110
car a=55 mph
car b=55-20, or 35 mph
check
In 3 hours, car a has gone 55*3=165 miles
car b has gone 35*3=105 miles
They add to 270 miles