math
posted by Julie .
can someone please help me, Rob is going to college in Oklahoma which is 680 miles from their his home in Tennessee. He can travel on state highways at 55mph or on the interstate at 70mph. Approximately, how much longer will his trip be if he takes state highways?
A. 5 hrs 3 min
B. 4 hrs 13 min
C. 3 hrs 5 min
D. 2 hrs 39 min

Have you considered using the equation
time=distanc/speed
figure the time for each, and subtract. 
Yes. 3 hours, 5 minutes is correct.