percent means partst out of 100 so
x%=x/100
ok so lets say
how to find total
total=how much you spent+(how much you spent times tax percent)
you can use distributive proerty to undistribute the 'how much you spent' (like ba+ac=a(b+c)) to get
total=how much you spent times (1+tax percent)
so what you do is
you know
how much you spent
tax percent so
1. convert tax percent to deceimal
2. plug into foormula
total cost=how much spent times (1+taxindecimalform)