Question 272435
P=100h/h+20
p=100*10/(10+20)
p=1,000/30
p=33.3% OF HOMES RECEIVE THEIR BOOKS IN 10 HOURS.
P=100*50/(50+20)
P=5,000/70
71.4 % IN 50 HOURS.
P=100*90/(90+20)
P=9,000/110
P=81.2 % IN 90 HOURS. 
80=100*H/(H+20)
80(H+20)=100H
80H+1600=100H
80H-100H=-1600
-20H=-1600
H=-1600/-20
H=80 HOURS SHOULD BE THE REQUIRED TIME FOR 80% TO RECEIVE THEIR BOOKS.