Question 293834
Two cars leave an intersection.
 One car travels north; the other east.
: 
When the car traveling north had gone 12 miles,
 the distance between the cars was 4 miles more
 than the distance traveled by the car heading east.
:
 How far had the eastbound car traveled? 
:
Let x = distance traveled by the eastbound car
then
(x+4) = distance between the cars when the northbound car has traveled 12 mi
:
This is a right triangle problem; c^2 = a^2 + b^2 
where
a = 12 mi
b = x
c = (x+4)
:
(x+4)^2 = 12^2 + x^2 = 
:
x^2 + 8x + 16 = 144 + x^2
:
x^2 - x^2 + 8x = 144 - 16
:
8x = 128
x = {{{128/8}}}
x = 16 mi is the distance of the eastbound car
:
:
See if that's true, distance between the cars should be 16+4 = 20 mi
12^2 + 16^2 = 20^2
144 + 256 = 400