Đáp án + Giải thích các bước giải:

Assume: Harry initially had `x` dollars`.`
`-` Harry spent ` \frac{1}{4} ` of his money on a book`.`
$\Rightarrow \text{Money spent on the book} = \frac{1}{4} x$
After buying the book`,` the remaining amount of money was`:`
$x - \frac{1}{4} x = \frac{3}{4} x$
`-` Harry then spent \( \frac{1}{2} \) of the remaining money on a watch`.`
$\Rightarrow \text{Money spent on the watch} = \frac{1}{2} \times \frac{3}{4} x = \frac{3}{8} x$

After buying the watch`,` the remaining amount of money was`:`
$\frac{3}{4} x - \frac{3}{8} x = \frac{3}{8} x$
`-` Harry had $27 left after these expenses`.`
`=>`$\frac{3}{8} x = 27$
`=>`$x = 27 \times \frac{8}{3} = 72$
So, Harry had $72 initially.

The amount after she bought a book :

`1-1/4=3/4` (amount of money)

The fraction representing the amount of money Harry spent on buying the watch is:

`3/4 ×1/2=3/8`

The fraction representing the amount of money Harry has left after buying the books and watch is:

`1-1/4-3/8=3/8`

her original amount:

`27 : 3/8=72` `$`

   Answer: `72$`