An extra-curricular book, I have read 100 pages, 25% more than others. How much is this book?
How many pages are left: 100÷( 1+25%)=80 pages.
How many pages does this book have * * *: 100+80= 180 pages?
Checking calculation: 80+80
x25
%= 100
A: This book has 180 pages.