Question 359743
Find the intercepts.
Plot them, then connect them with the line.
To find the x-intercept, set {{{y=0}}} and solve for {{{x}}}.
{{{3x+y=7}}}
{{{3x+0=7}}}
{{{3x=7}}}
{{{x=7/3}}}
({{{7/3}}},{{{0}}})
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To find the y-intercept, set {{{x=0}}} and solve for {{{y}}}.
{{{3x+y=7}}}
{{{0+y=7}}}
{{{y=7}}}
({{{0}}},{{{7}}})
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{{{drawing(300,300,-5,5,-2,8,circle(7/3,0,0.2),circle(0,7,0.2),grid(1),graph(300,300,-5,5,-2,8,-3x+7))}}}
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Typically parallel lines have identical slopes.
However in this case, the slope for {{{x+2=0}}} or {{{x=-2}}} is undefined. 
It is a vertical line and cannot be represented with the slope intercept form, {{{y=mx+b}}}.
It has the form {{{x=a}}} and since it passes through the point (-1,0), it has the exact form of {{{x=-1}}}.
{{{drawing(300,300,-5,5,-5,5,grid(1),blue(line(-1,10,-1,-10)),green(line(-2,10,-2,-10)),graph(300,300,-5,5,-5,5,0))}}}
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