algebra
posted by BC .
A car is traveling 60 mph. A truck leaves 7 minutes later and is traveling 70 mph. How long before truck will pass car?

distancecar= 60*t/60=t
distancetruck=70(t7)/60 where is in minutes.
at passing, the distances are equal. set them equal and solve for time t.
t=7/6t49/60
1/6t=49/60
t=4.9 minutes
check my work. 
oops, error.
t=7/6 t 49/6
now solve for t 
I would do it a different way. Since the car has a 7 Min headstart, traveling at 60mph, you can figure the distance it is ahead of the truck. Then, with the truck overtaking the car, by 10mph, you can figure the time it would take, going 10mph to go this headstart distance.