JAMB 2014 · UTME · Q24

Find the value of $\begin{vmatrix} 0 & 3 & 2 \\ 1 & 7 & 8 \\ 0 & 5 & 4 \end{vmatrix}$ .

Worked solution (try it first)

The first column is $(0, 1, 0)$ , so expand down it: only the middle entry, 1, gives a term.
Its place sign is $-$ (row 2, column 1).
Its minor, crossing out row 2 and column 1, is $3 \times 4 - 2 \times 5 = 2$ .
So the determinant is $-1 \times 2 = -2$ , option A.