10 − 4.

**The reasoning** This is straightforward subtraction: **10 − 4 = 6** Think of it visually: if you have 10 naira and spend 4 naira, you're left with 6 naira. Or count backward from 10: "9, 8, 7, 6" — that's four steps back, landing on 6. The principle here is **basic subtraction** — taking away a smaller number from a larger one to find the difference. **Why the wrong options tempt you** - **Option A (4)**: You might confuse this with "What number did we subtract?" The 4 is what we *removed*, not what remains. - **Option B (5)**: Careless counting or rushing can make you miscount by one. - **Option D (7)**: A common error is subtracting 3 instead of 4, especially under exam pressure when you misread the question. **Quick takeaway** When subtracting, the answer is always *what's left over*, not what you took away — always double-check you've subtracted the exact number shown.