The cost of a spa treatment is $42 and there is sales tax of 6%. What is the total cost of the spa treatment?

$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.

Step-by-step explanation:

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