Question

how to work out what is the larger 7/8 - 8/9

Answer 1

8/9 is the larger. 8/9 - 7/8 =  64 /72 - 63/72 = 1/72.

Answer 2

[$\frac{7}{8}=\frac{7\cdot9}{8\cdot9}=\frac{63}{72}\\\\\frac{8}{9}=\frac{8\cdot8}{9\cdot8}=\frac{64}{72}\\\\\frac{63}{72} < \frac{64}{72}\to\frac{7}{8} < \frac{8}{9}$