Part three is the correct answer for the questions of an and
Let x be the original number of chocolates:-
x - (2/3)x - (1/5)(x - (2/3)x) = 12
x - (2/3)x - (1/5)x + (2/15 )x = 12
15x - 10x - 3x + 2x = 180
4x = 180
x = 45
original amount of chocolates = 45
I know one of them is 1/2