the equation above is a LINEar equation, namely it's the equation of a line, and to graph a line all you need is two points, recall two points make up a line.
so, we can simply pick two random values for either. hmmm say "x", let's use hmmm values of 0 and 6 for example, we could have used any other two, but for simplicity let's use those,
[tex]\bf \stackrel{x=0}{-14(0)+21y=84}\implies 21y=84\implies y=\cfrac{84}{21}\implies y=4
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\textit{then that gives a point of }\qquad \qquad \boxed{(0~,~4)}\\\\
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\stackrel{x=6}{-14(6)+21y=84}\implies -84+21y=84\implies 21y=168
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y=\cfrac{168}{21}\implies y=8\qquad \textit{that gives use the point of}\qquad \qquad \boxed{(6~,~8)}[/tex]
so, plot those on the grid, and draw a line through them.
