Posted by Emily on Sunday, April 19, 2009 at 9:17pm.
Solve for X using the sidesplitting theorem for a triangle: upper left= 6x10, upper right= 5x, lower left= 4x+8, lower right=4x

MathGeometry  Reiny, Sunday, April 19, 2009 at 10:07pm
set up the proportion
(6x10)/(4x+8) = 5x/(4x)
the x's on the right side will cancel, then crossmultiply, it solves very nicely
I had x = 20