Question 1079370
<pre><b>
{{{drawing(1000/3,400,-2,8,-7,5,

locate(2,-5,"A(2,-5)"),locate(6.1,3,"B(6,3)"),
locate(6,-5,"C(6,-5)"),
locate(30/7,-3/7-.03,D), locate(6.1,-3/7,E),

grid(1),blue(triangle(2,-5,6,3,6,-5),

triangle(2.01,-5.01,6.01,3.01,6.01,-5.01)

triangle(2+.03,-5+.03,6+.03,3+.03,6+.03,-5+.03),
triangle(2-.03,-5-.03,6-.03,3-.03,6-.03,-5-.03),
triangle(2+.04,-5+.04,6+.04,3+.04,6+.04,-5+.04),
triangle(2-.04,-5-.04,6-.04,3-.04,6-.04,-5-.04),
line(30/7+.04,-3/7+.04,6+.04,-3/7+.04),line(30/7-.04,-3/7-.04,6-.04,-3/7-.04),
line(30/7,-3/7,6,-3/7)




)
 


 )}}}

I plotted the points on graph paper and called them A and B and drew AB.  
I drew the vertical line BC and the horizontal line AC, making right 
triangle ABC.

I guessed about where the desired point D would be and drew DE parallel
to AC.

Counting blocks, I noticed that BC = 8 and AC = 4.

By similar triangles DBE and ABC, {{{"BD"/"DA"="BE"/"EC"=3/4}}}

BE + EC = BC = 8

EC = 8 - BE

{{{"BE"/"EC"=3/4}}} 

{{{4*"BE"=3*"EC"}}}

{{{4*"BE"=3*(8-"BE")}}} 

{{{4*"BE"=24-3*"BE"}}}

{{{7*"BE"=24}}}

{{{"BE"=24/7}}}}

E is 24/7 units below B, so its y-coordinate is 

{{{3-24/7=21/7-24/7=-3/7}}}

That's also the y-coordinate of D.  We need
the x-coordinate of D, so we need to find DE.

By similar triangles DBE and ABC, 

{{{"DE"/"AC"="BE"/"BC"}}}

{{{"DE"*"BC"="BE"*"AC"}}}

{{{"DE"*8=expr(24/7)*4}}}

{{{"DE"*8=96/7}}}  

{{{"DE"=12/7}}}

Since D is 12/7 units left of E, which has
x-coordinate 6, the x-coordinate of D is

{{{6-12/7=42/7-12/7=30/7}}}

Therefore the answer is

{{{matrix(1,3,

D,""="",(matrix(1,3,30/7,",",-3/7)))}}}

Edwin</pre>