answer  thi  The  dimension  of  a  photogragh  is  30cm  X  20cm  what  lenth  of  wooden  frame  is  needed  ?

If the question is, "The  dimension  of  a  photograph  are 30cm  X  20cm. What is the length of the wood required to make its frame?"  then it can be solved as,

It is clear that,  Length of the wood required to make the frame is  equal to the perimeter of the photograph

⇒  Length of the wood required= 2×(30+20) cm

                                                 = 100 cm