what is x? where would i find it?는 무엇이고 내가 그것을 어떻게 찾을까?

If you are implying that the triangles are similar, then the short and long legs are in proportion:
[tex]3\div 2 = x\div 8[/tex]
Solving for x, you have
[tex]x = \dfrac{8\cdot 3}{2} = 12[/tex]