Question 1013289


if {{{77+81 =158}}}  and promotion mark was {{{80}}}%  

then {{{89+81 =170}}}  was {{{x}}}% 

since proportional, we have

{{{ 158/170=80/x}}}

{{{158x=80*170}}}

{{{158x=13600}}}

{{{x=13600/158}}}

{{{x=86.08}}}%