hi can you help me with this problem please, thank you.-----------------

If the speed of an experimental car is decreased by 8km/h it completes a 140 km trip in 2 hours more than had it been traveling at its usual speed. Determine its usual speed.

Let S=usual speed,
Then S-8=experimental speed.
Taking the difference between the "experimental time" and "usual time", we get:
140/S - 140/(S-8) = 2
Solve for S.