Question 861765
The answer is 52.
r*t=d
r=d/t

To get average speed you take total distance /total time=average speed
90/60=1.5 hours
40/40=1
1+1.5=2.5 hours

90+40=130
130/2.5=52
the book is wrong.
They must have changed the problem and forgot to change the solution and choices.
Unfortunately that happens all too often.

Double check the numbers and make sure you copied them correctly.