Question 937461
Draw the figure:
Show the perpendicular bisector segment with the endpoints the midpoint of the base and the apex vertex (the vertex of the triangle between the two equal sides).  This shows you two congruent right triangles.  
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Label some parts:
Altitude of the triangle, which is the segment described above;
x, the short leg of a right triangle;
h, the hypotenuse of a right triangle.


The base of the isosceles triangle is 2x.


Your triangle (the given isosceles triangle) has perimeter {{{h+h+2x=16}}}.


The given triangle has area  {{{(1/2)(2x)h=12}}}.


Solve for h and x...