Whole number plus fraction: 2 + 3/4
Keep the whole and the part side by side — 2 3/4 — or rewrite the whole as 8/4 and add for the single fraction 11/4.
The mixed-number form is the natural stop for reading and measuring; the single fraction is the form the next calculation wants.
Two whole bars and three quarters of another bar. Nothing overlaps, so the wholes just wait while the part hangs on.