To solve this problem you must apply the proccedure shown below:
1. The problem says that she had $240 to spends on gifts. When she bougth 8 identical statues she had $72 leftover. Therefore, let's call the cost of each statue [tex]x[/tex].
2. Now, you must substract $72 and $240 and divide this by 8 statues:
[tex]x=\frac{240-72}{8}\\x=\frac{168}{8}\\x=21[/tex]
Therefore, the answer is: $21.