Let the number of cookies in each tins is x.
Then the number of cookies in 8 tins = 8x.
Given, he took 15 cookies from each tin therefore he took
8 * 15 = 120 cookies from 8 tind
Hence, the total number of cookies left in 8 tins = 8x - 120
Given the left cookies in 8 tins is equal to the total number
of cookies in 2 of the tins at first
That is left cookies in 8 tins = 2x.
Hence, 8x - 120 = 2x => 6x = 120
=> x = 20
Hence, 20 cookies are there in each tin at first.