Question 238344
Let {{{x}}} = the original price of the knife
given:
The discount = {{{.1x}}}
The discounted price = {{{x - .1x}}}
{{{x - .1x = 500}}} dollars
{{{x*(1 - .1) = 500}}}
{{{.9x = 500}}}
{{{x = 555.56}}} 
{{{555.56 - 500 = 55.56}}}
Lucy saved $55.56