Question 188040
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Take given: (x1,p1)=> (42,$20);; (x2,p2)=> (52,$10)
We get the Slope via Point Slope Form {{{system(m=(p[2]-p[1])/(x[2]-x[1]))}}}
Substituting,
{{{m=(10-20)/(52-42)=-10/10=(red(-1))}}}


Thru point (42,20) via Slope-Intercept Form, y=mx+b  ==> p=mx+b
{{{20=(-1)(42)+b}}}
{{{20=-42+b}}} ---> {{{b=20+42=62}}}, Price (Y) Intercept


*Also the same when you try point (52,10) for the Price Intercept.


It follows ==> <font color=red>p=-x+62</font>, Answer

We see graph,
{{{drawing(500,500,-5,66,-5,77,grid(1),graph(500,500,-5,66,-5,77,-x+62),blue(circle(42,20,.5)),green(circle(52,10,.5)),green(locate(32,12,x[2](52)=p[2](10))),red(locate(44,23,x[1](42)=p[1](20))))}}}


Thank you,
Jojo</font>