Question 731499


let two numbers be {{{x}}} and {{{y}}}

if their sum is {{{12}}} we have 

{{{x+y=12}}}.....eq. 1

 and if their difference is {{{4}}} we have

{{{x-y=4}}}.....eq. 2

solve the system:

{{{x+y=12}}}.....eq. 1
{{{x-y=4}}}.....eq. 2
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{{{x+y=12}}}.....eq. 1...solve fo {{{y}}}

{{{y=12-x}}}.......substitute in eq. 2

{{{x-(12-x)=4}}}.....eq. 2.....solve fo {{{x}}}

{{{x-12+x=4}}}

{{{2x=4+12}}}

{{{2x=16}}}

{{{x=16/2}}}

{{{highlight(x=8)}}}

now find {{{y}}}

{{{y=12-x}}}

{{{y=12-8}}}

{{{highlight(y=4)}}}