Math  8th grade  Please help
posted by Chris on .
I don't know the formula to figure this out.
Charlie and Peter are driving around a racetrack. Charlie drives at an average speed of 108 miles per hour. Peter drives at an average speed of 99 miles per hour. Peter is given a head start of 12 miles. Charlie and Peter finish at the same time. How far does Charlie drive?
126,132,144 or 156 miles

Peter drives 12 miles less than Charlie.
they both drive the same time
so, if Charlie drives c miles,
and since time = distance/speed,
c/108 = (c12)/99
99c = 108(c12)
9c = 1296
c = 144 miles