We Cannot conclude that triangles DEF and LNM are similar if DF = 8 and LM = 4.
Solution:
Given that for two triangle DEF and LNM, DE = 8 and LM = 4.
To say that two triangles are similar the provided information is not complete.
Two triangles DEF and LNM , will be similar if there corresponding sides are in ratio which means

But we have only information of

But do not have any information regarding two remaining ratios that are

Hence cannot conclude that triangles DEF and LNM similar if DF = 8 and LM = 4