Mark paid $21.30 including tax for a shirt if he was charged 6.5% sales tax, how much did the shirt cost? ! also if you could explain how you got the answer!

21.30^ 65/1000 = 1,3845 ( sales tax )
21.30-1,3845= 19.91 ( shirt )

I got 65/1000 is because it’s a decimal if you have a decimal and you want to make it to a whole number you have to times the denominator and the numerator with the same number and when u find the tax price u just substract the after tax price of the shirt

The surface area would be 576 because you multiply all the numbers then multiply that number by 6