jenny had driven for 2h at a constant speed when road forced to reduce her speed by 10 mp/h for the remaining 1h of 152 mile trip. find her original speed

Question

152 - 10 = 142/2 = 71 mp/h

Can 71 mi/hr be right for the first speed?
71 mi/hr x 2 hrs = 142 miles traveled.
10 mi/hr x 1 hr = 10 miles traveled.
So we have 152 miles traveled in three hours BUT the second speed is not 10 mi/hr less than the original speed. In fact it is 71-10 = 61 mi/hr less. I think this answer is flawed.