Question 1132494
given:

 you pay ${{{55.00}}} for a backpack that has been discounted {{{15}}}%=> 

so, you actually pay {{{85}}}% of the original price and it is ratio {{{85/100}}}

if  the original price of the backpack was ${{{x}}}, we have

{{{85/100=55/x}}}


{{{85x=5500}}}

{{{x=5500/85}}}

{{{x=64.70588235294118}}}

${{{x=64.71}}}
 

check your work:

the original price of the backpack is ${{{x=64.71}}}

find  {{{15}}}% of the original price:   ${{{0.15x=64.71*0.15=9.705882352941176=9.71}}}

deduct discount from the original price:

${{{64.71-9.71=55}}} which confirms your solution