prealgebra
posted by Martin .
your family is driving to houston,texas.A sign indicates that you are 700 miles from houston.Your car's trip odometer indicates you are 400 miles from home.YOu are traveling at an average speed of 60 miles per hour.
A. write an expression for the distance(in miles) you will be from houston in x hours
B. Write an expression for the distance (in miles) you will be from home in x hours.
C. use the expressions from parts (a) and (b) to write and solve an equation to find the number of hours you will drive until you are exactly halfway between houston and your home.
D. suppose you travel by local roads instead of the highway.you travel the 700 miles at a speed of 45 miles per hour.How long will you drive before you are exactly halfway between houston and your home?
please help me.
i tried to do this already
and nobody has helped me

I am sorry my previous attempt to help you was not understood.
http://www.jiskha.com/display.cgi?id=1228878914.1228879850
I did my best to explain the logical steps, but apparently failed. If you could possible afford a private tutor who can spend more time with you, it would help a lot. 
Start by writing basic equations