We have the following:
Restarurant bill = $84.97
the tip is a value above the bill, that is, an extra percentage, as follows:
[tex]T=b+b\cdot t[/tex]
Where T is the total, b is the bill and t is the tip (%)
replacing:
For 20%:
[tex]\begin{gathered} T=84.97+84.97\cdot0.20 \\ T=101.96 \end{gathered}[/tex]
When the tip is the 20%, the estimate value is $101.96
For 10%:
[tex]\begin{gathered} T=84.97+84.97\cdot0.10 \\ T=93.47 \end{gathered}[/tex]
When the tip is the 10%, the estimate value is $93.47
