Shaan spend 3/4 of her pocket money dhe spend 1/2 on the book and 1/6 on the movie and the rest on the dress what part of her pocket money did she spend on dress

If she spent 1/2 OF HER POCKET MONEY on the book and 1/6 OF HER POCKET MONEY on the movie, and you want to find out what part OF HER POCKET MONEY did she spend on the dress

Amount she spent on dress
= 3/4 - 1/2 - 1/6
= 9/12 - 6/12 - 2/12
= 9/12 - 8/12
= 1/12 OF HER POCKET MONEY

If she spent 1/2 OF WHAT SHE SPENT IN TOTAL on the book and 1/6 OF WHAT SHE SPENT IN TOTAL on the movie, and you want to find out what part OF HER POCKET MONEY did she spend on the dress.

Amount she spent on the dress
= 3/4 - (1/2 x 3/4) - (1/6 x 3/4)
= 3/4 - 3/8 - 1/8
= 6/8 - 3/8 - 1/8
= 2/8
= 1/4 OF HER POCKET MONEY

Stating what the fraction is part of is very important, or else the answer can be affected. So choose which one your question was asking

Whose mistake? can you give more details to what the question is asking?