Question 176174
1.{{{7x-2y=8}}} 
2.{{{-14x+4y=8}}}
Double eq.1 and add to eq. 2 to get rid of x.
{{{2(7x-2y)+(-14x+4y)=2(8)+8}}}
{{{14x-4y-14x+4y=16+8}}}
{{{0=24}}}
Inconsistent system, there is no solution. 
These are two parallel lines that never meet, hence no solution.
{{{ graph( 300, 300, -5, 5, -10, 10, (8-7x)/(-2), (8+14x)/4) }}}
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3.{{{7x-2y = 8}}} 
4.{{{-14x+4y = -16}}} 
Double eq.3 and add to eq. 4 to get rid of x.
{{{2(7x-2y)+(-14x+4y)=2(8)-16}}}
{{{14x-4y-14x+4y=16-16}}}
{{{0=0}}}
Consistent, dependent system, there are infinite solutions. 
These two lines are actually the same line. So all of the points on the line solve this system of equations. 
{{{ graph( 300, 300, -5, 5, -10, 10, (8-7x)/(-2)) }}}
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5.{{{3x-2.5y=7.125}}}
6.{{{5x - 3y = 7.3125}}}
Let's multiply eq. 5 by 5 and eq. 6 by 3,then subtract to get rid of x.
{{{5(3x-2.5y)-3(5x-3y)=5(7.125)-3(7.3125)}}}
{{{15x-12.5y-15x+9y=35.625-21.9375}}}
{{{-3.5y=13.6875}}}
Change both left and right hand sides to a fractions before continuing,
{{{-(7/2)y=13+11/16}}}
{{{-(7/2)y=208/16+11/16}}}
{{{-(7/2)y=219/16}}}
{{{y=-219/16*(2/7)}}}
{{{y=-219/16*(2/7)}}}
{{{y=-219/56}}}
From eq. 6,
6.{{{5x - 3y = 7.3125}}}
{{{5x-3(-219/56)=7+5/16}}}
{{{5x+657/56=7+5/16}}}
{{{5x+657/56=112/16+5/16}}}
{{{5x+657/56=117/16}}}
{{{5x=117/16-657/56}}}
{{{5x=(117/16)(7/7)-(657/56)(2/2)}}}
Common denominator is 112. 
{{{5x=819/112-1314/112}}}
{{{5x=-495/112}}}
{{{x=-99/112}}}
{{{ graph( 300,300, -2, 2, -5, 1, (7.125-3x)/(-2.5), (7.3125-5x)/(-3)) }}}

or approximately,
x=-.89
y=-3.91