Evan, a business development representative of a leading pharmaceutical firm, took his client out for a dinner that cost $172.05 before taxes. If the tax was $23.50, calculate the tax rate.
The total cost of the dinner including taxes is $172.05 + $23.50 = $<<172.05+23.5=195.55>>195.55
The tax rate is $23.50 / $195.55 * 100 = 12%. Answer: \boxed{12}.