Borrowed book

Jane must, as soon as possible, return a borrowed book. She figured that reading 15 pages a day return the book in time. Then she read 18 pages a day and then returned the book one day before. How many pages should a book have?

Correct answer:

p =  90

Step-by-step explanation:


15d = p
18(d-1)=p

15·d = p
18·(d-1)=p

15d-p = 0
18d-p = 18

Pivot: Row 1 ↔ Row 2
18d-p = 18
15d-p = 0

Row 2 - 15/18 · Row 1 → Row 2
18d-p = 18
-0.17p = -15


p = -15/-0.16666667 = 90
d = 18+p/18 = 18+90/18 = 6

d = 6
p = 90

Our linear equations calculator calculates it.



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