Apack of 9 toilet rolls costs £4.23
a pack of 4 toilet rolls costs £1.96
which pack gives the better value for money

 a)  9 toilet rolls cost $ 4.23
       1 toilet roll costs  $ x

          9x = 4.23 * 1
           x= 4.23 / 9
            x = 0.47
So in first case one toilet roll costs $ 0.47.

b) 4 toilet rolls cost $1.96
    1 toilet roll costs  $ x
     
    4x = 1.96 * 1
     x = 1.96 / 4
     x = 0.49
So in second case one toilet roll costs $ 0.49.

0.47 < 0.49
The toilet roll in first case is cheaper than the toilet roll in second case.

Hope this heps!