<PRE><B>Question 314018</B>
 Two cars leave an intersection. One car travels north; the other east.
 When the car traveling north had gone 9 miles, the distance between the cars was
 3 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+3) = distance between the cars when the northbound car had traveled 9 mi
:
A pythag problem a^2 + b^2 = c^2
where
a = x
b = 9
c = (x+3)
:
x^2 + 9^2 = (x+3)^2
x^2 + 81 = x^2 + 6x + 9
Combine on the left
x^2 - x^2 - 6x + 81 - 9 = 0
-6x + 72 = 0
-6x = -72
x = {{{(-72)/(-6)}}}
x = +12 mi traveled by the eastbound car
:
:
Check: 
12^2 + 9^2 = 15^2</PRE>