Answer
2.75 mph for faster group
2.25 mph for slower group
Work Step by Step
1200 miles, 240 hours
distance = rate * time
Group A: $d = x*240$
Group B: $t = (x-.5)*240$
$d+t=1200$
$240x+(x-.5)*240=1200$
$240x+240x-120=1200$
$480x=1320$
$480x/480 = 1320/480$
$x=2.75$
$2.75-.5=2.25$
