Using Statement-I alone: From Statement-I, we have X = $(4/5) \times (Y + Z)$, or X = $4k$ and $(Y + Z) = 5k$. This gives us the relationship between X, Y, and Z but does not allow us to determine who received the least. Thus, Statement-I alone is insufficient.

Using Statement-II alone: From Statement-II, we have Y = $(2/7) \times (X + Z)$, or Y = $2k$ and $(X + Z) = 7k$. This gives us the relationship between Y, X, and Z but does not directly provide the least amount. Hence, Statement-II alone is insufficient.

Combining Statement-I and Statement-II: From both equations:

• From Statement-I: X = $4k$ and $(Y + Z) = 5k$
• From Statement-II: Y = $2k$ and $(X + Z) = 7k$

Solving these gives:

• $Y + Z = 5k$
• $2k + Z = 5k$, so $Z = 3k$

Now we know X = $4k$, Y = $2k$, and Z = $3k$. Hence, X : Y : Z = $4 : 2 : 3$. Clearly, Y received the least amount.