Question 123052
If the triangle is isosceles, this means that TWO sides are equal.  If the base is 12, then let the two equal sides be x.  


The base is x-12


The sum of the three sides is 
x+x+x-12 = 39
3x-12=39
3x =39+12
3x=51
x=51/3
x=17 inches for each equal side
x-12= 5 inches = base


R^2