Answer: [tex]\$16\dfrac{9}{10}[/tex]
Step-by-step explanation:
Given
Hannah had 30 dollars
Money spent on gift A
[tex]8\ \dfrac{7}{10}=\dfrac{8\times 10+7}{10}=\dfrac{87}{10}[/tex]
money spent on gift B
[tex]4\ \dfrac{2}{5}=\dfrac{22}{5}[/tex]
Money spent on gift C
[tex]\Rightarrow \text{Total-Money spent on (A+B)}\\\\\Rightarrow 30-\dfrac{87}{10}-\dfrac{22}{5}=30-\dfrac{87}{10}-\dfrac{44}{10}\\\\\Rightarrow \dfrac{300-87-44}{10}=\dfrac{169}{10}\\\\\Rightarrow \$16\ \dfrac{9}{10}[/tex]