Final answer:
To find the purchase price of the router, subtract the sales tax from the total cost by dividing the sales tax by the sales tax rate and subtracting it from the sales tax. The purchase price of the router is $180.
Step-by-step explanation:
To find the purchase price of the router, we need to subtract the sales tax from the total cost. The sales tax is calculated by multiplying the sales tax rate (5.5%) by the total price of the router. In this case, the sales tax is $9.90. To find the total cost of the router, we can divide the sales tax by the sales tax rate (0.055) and then subtract it from the sales tax.
Total cost of the router = Sales tax / Sales tax rate = $9.90 / 0.055 = $180
Therefore, the purchase price of the router is $180.