Give data:
Bill =$90
Tip= 11 % of the bill
To get how much I will leave as a tip, I have derived a simple formula to be used:
[tex]\text{Amount}=\text{Bill}\times tip[/tex]Substituting the values from the given data, we will have
[tex]\begin{gathered} \text{Amount}=90\times11\text{ \%} \\ =90\times\frac{11}{100} \\ =\frac{990}{100} \\ \Rightarrow\text{ \$9.9} \end{gathered}[/tex]Therefore, the amount I will leave for tip will be $9.90