Assign the configuration of the stereocentre in the compound shown (butan-2-ol drawn with wedges).

CIP priorities at C2 of butan-2-ol: $\mathrm{OH}$ (O) is first, then $\mathrm{C}{}_2\mathrm{H}{}_5$ (C attached to C,H,H) over $\mathrm{CH}{}_3$ (C attached to H,H,H), and $\mathrm{H}$ last. With the $\mathrm{H}$ pointing away from the viewer, the sequence $\mathrm{OH}\to \mathrm{C}{}_2\mathrm{H}{}_5\to \mathrm{CH}{}_3$ runs clockwise in the drawing, so the configuration is $(R)$.