Let the speed for the first 12 mi be x mi/h, the speed for 18 mi was (x+4) mi/h
thus given that
time=distance/speed
the average time will be:
3=(12+18)/(x+x+4)
3=30/(2x+4)
solving for x we get
3(2x+4)=30
6x+6=30
6x=24
x=4 mi/hr
Answer: 12 mi/hr
Is this a question? Or what is the question if you first said it?
Sean read 15 of a book in = 112 hours,
so, 1 of a book in = 112/15
Now, 12 of a book would be: 112/15 * 12 = 112/5 * 4 = 89.6
89.6 = 89 6/10 = 89 3/5
In short, Your Answer would be 89 3/5 hours
Hope this helps!
