The total cost of 12Kg of apples and 24Kg of oranges is N21.60. The cost of 24Kg of apples and 12Kg of oranges is N18. Find the cost of apples per Kg.

Let $a$ be the cost of 1 Kg of apples in Naira (N).
Let $o$ be the cost of 1 Kg of oranges in Naira (N).

From the first statement, "The total cost of 12Kg of apples and 24Kg of oranges is N21.60":

$$12a + 24o = 21.60 \quad (1)$$

From the second statement, "The cost of 24Kg of apples and 12Kg of oranges is N18":

$$24a + 12o = 18 \quad (2)$$

To eliminate $o$, multiply equation (2) by 2:

$$2 \times (24a + 12o) = 2 \times 18$$ $$48a + 24o = 36 \quad (3)$$

$$(48a + 24o) - (12a + 24o) = 36 - 21.60$$ $$48a - 12a + 24o - 24o = 14.40$$ $$36a = 14.40$$

$$a = \frac{14.40}{36}$$ $$a = 0.40$$

The cost of apples per Kg is N0.40.

The final answer is $\text{N0.40}$.