Suppose the sides of the big triangle are called m, x and 12+4=16. We have that the big triangle and the small triangle to the right of the shape (sides x,y,12) are similar. We can take then the ratios of correponding sides and know that they will be equal. Thus, we have that 4/y=y/12. Hence, y*y=48. Thus y=[tex] \sqrt{48} = 4 \sqrt{3} [/tex].
