Question 719859
{{{ 3x + y = 9 }}}
{{{ 5x - y = 7 }}}
First put them both into the same form
(1) {{{ y = -3x + 9 }}}
(2) {{{ y = 5x - 7 }}}
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The slope of (1) is {{{ -3 }}}
The slope of (2) is {{{ 5 }}}
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The point where the lines intersect is 
the solution of the equations
To find the solution:
Add the equations as they are given originally
{{{ 3x + y = 9 }}}
{{{ 5x - y = 7 }}}
{{{ 8x = 16 }}}
{{{ x = 2 }}}
PLug this result back into either equation
{{{ 3*2 + y = 9 }}}
{{{ y = 9 - 6 }}}
{{{ y = 3 }}}
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This tells me the intersection is at ( 2,3 )
Here's the graph:
{{{ graph( 400, 400, -5, 5, -10, 10, -3x + 9, 5x - 7 ) }}}