<PRE><B>Question 883080</B>
6x (x being the miles per hour; 6 is the number of hours that car A traveled) + 4x (car B) = 550
6x+4x=550
10x=550
Divide each side by 10
x = 55 mph
.
Prove it.
Car A leaves the house at 10 am.  By 4 pm, he has traveled 6*55, or 330 miles
Car B leaves the house at 12 pm.  By 4 pm, he has traveled 4*55, or 220 miles.
330+220=550</PRE>