Question 651531


{{{x+y= 30}}}....1

{{{x-y= 12}}}....2
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you can solve this system by addition; add 1 and 2

{{{x+y= 30}}}....1
+
{{{x-y= 12}}}....2
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{{{x+x+y+(-y)=30+12}}}

{{{2x+cross(y)+(-cross(y))=42}}}

{{{2x=42}}}

{{{x=42/2}}}

{{{highlight(x=21)}}}

now find {{{y}}}

{{{21+y= 30}}}....1

{{{y= 30-21}}}

{{{highlight(y= 9)}}}