Question 1179647


let similar chocolate bars be {{{x}}} and similar packets of candy {{{y}}}

if {{{3}}} similar chocolate bars and {{{4}}} similar packets of candy weigh {{{200g}}}, we have

{{{3x+4y=200g}}}...solve for {{{x}}}
{{{3x=200g-4y}}}......eq.1

if {{{3 }}}such chocolate bars and {{{7}}} such packets of candy weigh {{{260g}}}, we have

{{{3x +7y=260g}}}.....solve for {{{x}}}
{{{3x =260g-7y}}}.......eq.2

from eq.1 and eq.2 we have
{{{200g-4y=260g-7y}}}
{{{7y-4y=260g-200g}}}
{{{3y=60g}}}
{{{y=20g}}}

go to
{{{3x=200g-4y}}}......eq.1, substitute {{{y}}}
{{{3x=200g-4*20g}}}......eq.1
{{{3x=200g-80g}}}
{{{3x=120g}}}
{{{x=40g}}}

 the weight of a chocolate bar is {{{highlight(40g)}}}, ->answer
and  the weight of a candy is {{{20g}}}