Question 1106449
x hours at 90 k/h for 90x km
3-x hours at 30 k/h for 90-30x km
That sum is 150
90x+90-30x=150
60x=60
x=1 hour at 90 k/h  for 90 km. ANSWER
3-x=2 hours at 30 k/h

If the book says 60 km in the storm, than that is 2/3 of an hour at 90 km/hr.  That would require 2 1/3 hours at 30 km/h, and that is 70 km, not 90.  The above answer I gave is correct
Hour 1--90 km
Hour 2--30 km
Hour 3--30 km
They add to 150 km