When VAT is added to a bill of £450 the final bill is £531.
What percentage is the final bill in VAT?
VAT = (531-450)/450*100 %
$${\mathtt{VAT}} = {\frac{\left({\mathtt{531}}{\mathtt{\,-\,}}{\mathtt{450}}\right)}{{\mathtt{450}}}}{\mathtt{\,\times\,}}{\mathtt{100}} \Rightarrow {\mathtt{VAT}} = {\mathtt{18}}$$
VAT = 18%
