Statement 1 is clearly insufficient. Using Statement 2, maybe her speed was 8 km/hr, and the total distance was 16 km, so took 2 hours. Then if her speed was 8 km/hr greater, so was 16 km/hr, she would have saved an hour. But we know there must also be a solution where her speed was 72 km/hr, because the two Statements must be logically consistent, and in that case the time will be much greater than 1 hour, so we've found two possible answers, and Statement 2 cannot be sufficient alone.

Using both Statements, if it took her t hours, the distance was 72t, from Statement 1, and 80(t-1) from Statement 2. These are equal, as Statement 2 tells us, so we get a simple equation in one unknown that we can clearly solve, and the answer is C.