4 1/8 + 5 3/ 4 = 33/8 + 23/4 = 33/8 + 46/8 = 79/8 = 9 7/8

[latex]4\frac{1}{8}+5\frac{3}{4}=4\frac{1}{8}+5\frac{3\cdot2}{4\cdot2}=4\frac{1}{8}+5\frac{6}{8}=9\frac{7}{8}[/latex]