Question 833053
The line a(12,x) and b(x,8) has a slope of -3/7 what is the value of x. How do I find it?<pre>We will change coordinate point a from (12, x) to (12, X), and coordinate point b from (x, 8) to (X, 8)
to avoid confusion
Formula for slope, or {{{m = (y[1] - y[2])/(x[1] - x[2])}}}, where:
{{{y[1] = X}}}
{{{y[2] = 8}}}
{{{x[1] = 12}}}
{{{x[2] = X}}}
Therefore, {{{m = (y[1] - y[2])/(x[1] - x[2])}}} becomes: {{{- 3/7 = (X - 8)/(12 - X)}}} 
7(X - 8) = - 3(12 - X) ------ Cross-multiplying
7X - 56 = - 36 + 3X
7X - 3X = - 36 + 56
4X = 20
{{{X = 20/4}}}, or {{{highlight_green(5)}}}
You can do the check!! 

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