Object A travels @ 70 mph, Object B @ 60 mph, but in opposite direction. So the relative speed of B from A's viewpoint is 70 + 60 = 130 mph. Distance to be covered = 260 miles.

As distance=speed x time, time= distance/speed, therefore time = 260 m/ 130mph = 2 Hours.

To prove this consider this ,

At time T0, A and B will be 260 miles apart

At time T1(lets say after 1 Hour), A will have travelled 70m and B will have travelled 60 miles. SO the remaining distance to be covered will be 260m - 70- 60 = 130 m

Again after another hour, A will have travelled 140 miles towards B and A will have travelled 120 miles towards A. So the total distance travelled is 140 + 120 = 260 miles in 2 Hours which is what we calculated

As distance=speed x time, time= distance/speed, therefore time = 260 m/ 130mph = 2 Hours.

To prove this consider this ,

At time T0, A and B will be 260 miles apart

At time T1(lets say after 1 Hour), A will have travelled 70m and B will have travelled 60 miles. SO the remaining distance to be covered will be 260m - 70- 60 = 130 m

Again after another hour, A will have travelled 140 miles towards B and A will have travelled 120 miles towards A. So the total distance travelled is 140 + 120 = 260 miles in 2 Hours which is what we calculated