Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
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Exercise 14 Page 345

The Triangle Midsegment Theorem tells us that, if a segment joins the midpoints of two sides of a triangle, then the segment is half as long as the third side.

x=12

Practice makes perfect

To find the value of x in the given diagram, let's start by labeling the vertices of each of the smaller triangles.

Looking at the markings, we can note a couple key congruence relationships. AX ≅ XB CY ≅ YB This means that X and Y are the midpoints of AB and CB, respectively. Therefore, XY is a midsegment of △ABC. The Triangle Midsegment Theorem tells us that, if a segment joins the midpoints of two sides of a triangle, then the segment is half as long as the third side. XY= 1/2 AC Finally, we will substitute the given values into this equation to find x.
XY=1/2AC
3x=1/2( 5x+12)
6x =5x+12
x=12