$45.19. First you multiply 39.99 by .13 then you add 5.1987 to 39.99 and then round it.
-
39.99 + 13% tax
=39.99 + 39.99*13/100
=39.99+5.1987
=45.1887
=39.99 + 39.99*13/100
=39.99+5.1987
=45.1887
-
13%=.13 so multiply 39.99 x .13 for the tax amount then add that to 39.99 for the total.
-
39.9*1.13 = 45.19
-
$45.19