radio was 10 got markup of 54% this implies it is almost 1/2x more than 10 10*1 is 100% of 10 use this fact and take 10 + .54*10=New Cost (nc) tax is 2% use nc*1.2

Price: 10.00$ The percentage that is off:54percent Tax:2percent. You need to add the tax(2%) to the markup(54%) and subtract that from the original cost