The moment of a force about a point, forces on a rectangular lamina, forces as vectors $a\mathbf{i} + b\mathbf{j}$ and couples, levelled, click to reveal
Moment $=$ force $\times$ perpendicular distance; for $a\mathbf{i} + b\mathbf{j}$ at $(x, y)$ the moment about $O$ is $xb - ya$ (anticlockwise positive)