Final Answer:
The store charged Monica $20.00 for the bike helmet before tax.
Step-by-step explanation:
We can use the formula: Sales Tax = Tax Rate * Price before Tax to solve for the price before tax.
Rearranging the formula to isolate the price before tax, we get: Price before Tax = Sales Tax / Tax Rate.
Substituting the known values: Price before Tax = $1.60 / 0.08 = $20.00.
Therefore, Monica paid $20.00 for the bike helmet before tax.