Question 108296
if you draw a picture you get a better idea. Call the first car Car A and the second Car B. Car A is moving 60mi/h from the house, and Car B is moving 50mi/h from the house the other direction. 

So, we can come up with 2 equations, one to describe each Car. Define Car A's motion to be positive, which means Car B's is negative as it's in the opposite direction. 
{{{
a=60t
}}}
{{{
b=-50t
}}}
so, we want to find when the distance between the two is 330. Distance is the absolute value of the difference. 
{{{
abs(a-b)=abs(60t-(-50t))=abs(110t)=110t
}}}
The absolute value drop as t must be positive (it's time). Then, we're looking when this distance is 330
{{{
110t=330
t=3
}}}
So the answer is 3 hours.