David knew he made a mistake when he calculated that Gilda walks 123 miles to the station. Read through David's calculations:

Using d = rt, the distance is the same, but the rate and time are different.

If Gilda misses the train, it means the time t needs 7 more minutes so d = 3(t + 7).

If she gets to the station 5 minutes early means the time t can be 5 minutes less so d = 4(t - 5).

3(t + 7) = 4(t - 5)

3t + 21 = 4t - 20

t = 41

d = rt, so d = 3(41) = 123

Find David's mistake in his calculations. In two or more complete sentences, explain his mistake. Include the correct calculations and solutions in your answer.