Question 1116924
1.{{{x+y=42}}}
2.{{{y+z=67}}}
3.{{{x+z=55}}}
Adding them all together,
{{{x+y+y+z+x+z=42+67+55}}}
{{{2x+2y+2z=164}}}
{{{x+y+z=82}}}
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.
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From 3,
{{{z=55-x}}}
Substituting into 2,
{{{y+(55-x)=67}}}
4.{{{-x+y=12}}}
Adding 1 and 4,
{{{x+y-x+y=42+12}}}
{{{2y=54}}}
Solve for y then use the other equations to solve for x and z.