Question 403382
(20,69)
(33,50) 
So x is units and y is price
{{{m=(y2-y1)/(x2-x1)=(50-69)/(33-20)=(-19/13)}}}
Use the point slope formula and plug in the slope and one of the points given
{{{y-y1=m(x-x1)}}}
{{{y-69=(-19/13)(x-20)}}}
{{{y-69=-19x/13+380/13}}} add 69 to each side
{{{y=-19x/13+380/13+69}}} simplify
{{{y=-19x/13+380/13+897/13}}}
{{{y=-19x/13+(380+897)/13}}}
{{{y=-19x/13+1277/13}}}
{{{ graph( 300, 200, -50, 100, -150, 150, -19x/13+1277/13) }}}