$35 bill before tax
tax:5.8%
Tip:21%

If tip goes only on amount but not on tax: $44.38

If tip goes on total including tax: $44.81

Step-by-step explanation:

If the tip is applied to the price before tax, then we need to add 5.8% and 21% of $35 to $35.

tax + tip = 5.8% + 21% = 26.8%

100% + 26.8% = 126.8% = 1.268

1.268 * $35 = $44.38

If the tip is applied to the price plus tax, then we calculate the amount including tax first, then we add the 21% tip based on that price.

Bill before tax: $35

Add 5.8% tax: 1.058 * $35 = $37.03

Add tip to the amount including tax: 1.21 * $37.03 = $44.81