Answer:
[tex]\large \boxed{5.0 \, \% }[/tex]
Step-by-step explanation:
1. Calculate the amount of tax
Total cost = selling price + sales tax
Sales tax = total cost - selling price
Total cost = $651
-Selling price = - 620
Sales tax = $ 31
2. Calculate the percent tax
[tex]\text{\% Tax} = \dfrac{\text{\$31}}{\text{\$620}} \times 100 \, \% = \mathbf{5.0 \, \%}\\\\ \text{The sales tax percentage is $\large \boxed{\mathbf{5.0 \, \% }}$}[/tex]