Since the line bisects the right angle of the larger triangle, the angle opposite 3 in the triangle on top is 45 degrees (90/2 = 45).
sin 45 = 3/x
[tex]\frac{1}{\sqrt{2} }[/tex] = [tex]\frac{3}{x}[/tex]
x = 3[tex]\sqrt{2}[/tex]
