Mary has two bags of sweets, each of which contains the same number of sweets. she eats four sweets. she then finds that she has 30 sweets left. how many sweets were in each bag to start with?

Given that Mary has 2 bags of sweets. each of which contains same number of sweets.

Let us assume each bag contains x  number of sweets.

After eating 4 sweets, total number of sweets left in two bags = x+x-4=2x-4

But given 2x-4 = 30

                2x-4+4 = 30+4

                 2x=34

Hence there are 17 sweets in each bag at starting.