Find the total cost of a spa treatment of $42 including 6% sales tax and 20% tip

Cost of the spa treatment = $42

Percentage of sales tax = 6%

Percentage of tips = 20%

Normally the tips amount is calculated before adding sales tax.

Then

Amount of tips given = (20/100) * 42

= (1/5) * 42

= 8.40 dollars

Amount of sales tax taken = (6/100) * 42

= 252/100

= 2.52 dollars

Then

The total amount spent for spa treatment = (42 + 8.40 + 2.52) dollars

= 52.92 dollars

So we can see that $52.92 has been spent in total for spa treatment and this amount includes a sales tax of $2.52 and a tip of $8.40.