3 1 — :— 8 3

It looks like you’ve given a 2x2 matrix: [ [3, 1], [8, 3] ]

Determinant formula for [ [a, b], [c, d] ] is ad − bc.

So det = 33 − 18 = 9 − 8 = 1.

Answer: 1

If you also need the inverse, since det = 1, the inverse is [[3, -1], [-8, 3]].