can any one tell me a way of working out a percentage from a total for tax purposes.

Example; if i have a total of 78 and the tax was 17.5% it would be
78 divide 47 x 7 =11.61

can anyone tell me how to work it out if the tax was 16%
thanks

"78 divide 47 x 7 =11.61 " ??????
I have no idea where you are getting that from.

17.5% of 78 = .175 x 78 = 13.65
16% of 78 = .16 x 78 = 12.48