Final answer:
Lena can calculate the total cost of the toy by adding the sales tax, which is 15% of $9 (converted to $1.35), to the original cost, giving her a total of $10.35. None of the provided equations correspond to the correct calculation.
Step-by-step explanation:
Lena wants to calculate the total cost of a soft toy after including a 15% sales tax on the base price of $9. To find the sales tax, we convert the percent to a decimal by dividing it by 100. Therefore, 15% becomes 0.15 when converted to a decimal. We then multiply this decimal by the cost of the toy to find the amount of sales tax.
Sales tax = Cost of the toy × Sales tax rate = $9 × 0.15 = $1.35
The next step is to add this sales tax to the original cost to find the total cost:
Total cost = Cost of the toy + Sales tax = $9 + $1.35 = $10.35
Therefore, none of the provided equations (A, B, C, D) accurately represent the calculation needed to find the total cost of the toy.