There are 3 thirds in one
My answer is 38 students
( 22 students take one or both subjects)
Let x be the page number then x+1 would be the other page number (because the pages are two facing pages which means they follow on consecutively)
Then
(x)(x+1) = 156
x^2 + x - 156 = 0
x = 12 or x = -13( but x can't be a negative number)
so x = 12
and the next page is 13
