Question 574164
{{{x+y=6}}}..............(1)
{{{y=2x}}}...............(2)

Put in the value of y from (2) to (1)
{{{x+2x=6}}}
{{{3x=6}}}
{{{3x/3=6/3}}}
{{{cross(3)x/cross(3)=cross(6)/cross(3)}}}
{{{x=2}}}
Put the value of x in (2)
{{{y=2(2)}}}
{{{y=4)}}}

x,y=2,4



Check
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Put the value of x and y in (1)
{{{x+y=6}}}..............(1)
{{{2+4=6}}}
{{{6=6}}}
Put the value of x and y in (2)
{{{y=2x}}}
{{{4=2(2)}}}
{{{4=4}}}