Find the dissimilar word. Y75, W68, U63, L36, R54

Let us check the relationship between the letter and the number for each pair using the standard positional values of letters ($\text{A}=1,\dots ,\text{Z}=26$):
* $\text{Y}=25⟹25\times 3=75$
* $\text{W}=23⟹23\times 3=69$ (but given as $68$)
* $\text{U}=21⟹21\times 3=63$
* $\text{L}=12⟹12\times 3=36$
* $\text{R}=18⟹18\times 3=54$
The pattern is $\text{Number}=\text{Position of Letter}\times 3$. W68 does not follow this pattern ($23\times 3=69$). Thus, W68 is the dissimilar one.