8th grade math
posted by stella .
One of your friends is heading north for
the Christmas holiday and the other friend
is heading south. If when they start,
they are 1029 miles apart and one car is traveling at 53 miles per hour, and the other 45 miles per hour, how many hours
before the two cars pass each other?

1,029 : (53 + 45) = 10.5
You don't know how long time will it take the cars to pass each other, so you assign letter "X" to the unknown time. Then multiply each car's speed by the time it would take for them to pass each other (e.g. by "X"). You'll get the following equation:
53x + 45x = 1,029
98x = 1,029
x = 1,029 / 98
x = 10.5