Question

After reading 7/9 of a book 40 pages are left.How many pages are their in a book?

Answer 1

$\frac{7}{9} \times x + 40 = x$
on solving, we get x= 180 pages.

Answer 2

Here is your answer-----

Let the total number of pages be x
=x-7/9*x=40
=(9x-7x)/9=40
=2x/9=40
=2x=40*9
=x=360/2
x=180

Hope it helps.... :))