Hey there!!
How do we know which value is better?
Ans : We compare the value for one tissue roll in each case.
1st case - 4 rolls cost 1.89
1 roll = 1.89 / 4
1 roll = 0.47
2nd case - 9 rolls cost 3.99
1 roll = 3.99 / 9
1 roll = 0.443
Both cases :
1 st case - 0.47
2 nd case - 0.443
0.47 > 0.443
Hence the second value is better than the first.
Hope my answer helps!!