Question 742022
Solve 5x+4y=12 and 3x+4y=4 by substitution? 


From the "4" equation, 
{{{4y=4-3x}}}
{{{4y(1/4)=4(1/4)-3(1/4)x}}}
{{{y=1-(3/4)x}}}


Using the "12" equation,
{{{5x+4(y)=12}}}
SUBSTITUTE FOR y found in "4" equation...
{{{5x+4(1-(3/4)x)=12}}}
{{{5x+4-3x=12}}}
.
Can you continue with this from there?
TRY ON YOUR OWN FIRST, AND THEN IF YOU NEED....





{{{5x+4-3x=12}}}
{{{5x-3x+4=12}}}
{{{2x=12-4}}}
{{{2x=8}}}
{{{highlight(x=4)}}}.


Back to the y from the "4" equation,
{{{y=1-(3/4)x}}}
{{{y=1-(3/4)(4)=1-3=-2}}}
{{{highlight(y=-2)}}}