Question

What is the final price of a 240 bike with a 3.5% tax

Answer 1

Assuming you mean $240 and not $2.40:

C - cost
P- Price
T- tax

P = C + C*T

P = 240 + (240)(0.035)
"=248.4"

Answer 2

240*0.035=?
You take the original price and mulitiply it by .035 and you get your answer.