Hi All,
I am confused with Understanding Inequalities Property in the below mentioned problem,

If 20 Swiss Francs is enough to buy 9 notebooks and 3 pencils, is 40 Swiss Francs enough to buy 12 notebooks and 12 pencils?
(1) 20 Swiss Francs is enough to buy 7 notebooks and 5 pencils.
(2) 20 Swiss Francs is enough to buy 4 notebooks and 8 pencils.

To Find: 12N+12P <=40 or 6N+6P<=20.

Given: 9N+3P <=20

So basically we want to find whether 3 Notebooks can be replaced by 3 Pens or not .

Statement 1: 7N+5P <=20

From above statement 1 I understood that we can substitute 2 Note books with 2 Pens. Then why can't we substitute 3 Note books with 3 pens ? so that A can be sufficient.

Solution says if we can substitute 5 Note books with 5 pens then we can substitute 3 note books with 3 pens but note vice-versa .

I couldn't understand can anyone please explain in elaborate way ?

Thanks in advance.

Regards,
Uva.