mike bought pizza in 12 pieces.he ate 1/6.his brother ate 1/5.

OK...I don't see a question here, but I will make some assumptions

Mike eats 1/6 of the 12 slices    1/6 x 12 = 2      so there are 10 pieces left

His brother eats 1/5 of what is left    1/5  x 10 = 2    so there are 8 pieces left.