Question 959019
First graph the line 
{{{y=3x+7}}}
When {{{x=0}}}
{{{y=3(0)+7=7}}}
(0,7)
When {{{x=-2}}}
{{{y=3(-2)+7=-6+7=1}}}
(-2,1)
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.
.
{{{drawing(300,300,-8,8,-4,12,grid(1),circle(0,7,0.25),circle(-2,1,0.25),graph(300,300,-8,8,-4,12,3x+7))}}}

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Now choose a point not on the line.
(0,0) is convenient.
Test the inequality.
If it's true, shade the region containing (0,0).
If it's false, shade the other region.
{{{y<3x+7}}}
{{{0<3(0)+7}}}
{{{0<7}}}
True.
{{{drawing(300,300,-8,8,-4,12,grid(1),circle(0,7,0.25),circle(-2,1,0.25),graph(300,300,-8,8,-4,12,y<3x+7))}}}