Apackage of aa batteries costs 3.50 plus an additional 6% tax. what is the price after tax?

6% tax means 6% of $3.50

Convert 6% to decimal (move decimal 2 spots to the left): 6% ⇒ .06

Multiply 3.50 with .06 = .21 <-- That's .21 cents of 3.50

That means you have to pay an extra 21 cents. Add that to the $3.50 you had to pay.

$3.50 + $0.21 = $3.71 <-- Price after tax