Larry C. answered • 9d

Computer Science and Mathematics professional

If x is Casey's speed, then x+9 is Sam's speed.

In 3 hours, Casey travels 3x miles and Sam travels 3x+27 miles.

Since together they traveled 99 miles:

99 = 3x + 3x + 27 -> 72 = 6x -> 12 = x

So Casey traveled 12 mph and Sam 21 mph.