Question 157338
{{{18X + Y = 42}}}---------> eqn 1, {{{6X - 3Y = -6}}} -----------> eqn 2
In eqn 1 we get,
{{{Y=42-18X}}} ----------> eqn 3
Susbtitute eqn 3 in eqn 2:
{{{6X-3(42-18X)=-6}}}
{{{6X-126+54X=-6}}}, combine similar terms
{{{6X+54X=-6+126}}}
{{{60X=120}}} ----> {{{cross(60)X/cross(60)=cross(120)2/cross(60)}}}
{{{X=2}}}
For {{{Y}}} go back eqn 3:
{{{Y=42-18*2=42-36=6}}}
In doubt? go back eqn 1:
{{{18*2+6=42}}}
{{{36+6=42}}}
{{{42=42}}}
Also via eqn 2:
{{{6*2-3*6=-6}}}
{{{12-18=-6}}}
{{{-6=-6}}}
Thank you,
Jojo