Pythagorean Theorem: in a right triangle, the sum of the squares of the sides = the square of the hypotenuse. Cars drive distance A (6) turn left and drive distance B (8). (6*6)+(8*8)=100. Sqroot of 100 is 10, the distance is double since we're talking about 2 cars, therefore answer is 20.
And that's about all the trig I remember. :)