two trains leave the station at the same time. the first train is traveling north and the second train is traveling south 20 mph slower. after 2 hours, they are 180 miles apart. how fast is each train moving? so much!

To work out speeds you need to know the distance that each train has travelled.
So an equation needs to be formed
x = distance of slower train
x + 40 = distance of faster train   (it is + 40 as the trains were travelling for 2 hours not one hour so 20 x 2 = 40)

so, x + x + 40 = 180
2x + 40 = 180
2x = 140
x = 70

Distance of slower train = 70 miles
Distance of faster train = 70 + 40 = 110 miles

To work out speed divide the distances by 2 as speed = distance/time

speed of slower train = 70/2 = 35mph
speed of faster train = 110/2 = 55mph