2-7/9= is what
This is how I would do it.
$$2-\frac{7}{9}$$
$$\\=1+1-\frac{7}{9}\\\\=1+\frac{9}{9}-\frac{7}{9}\\\\=1+\frac{2}{9}\\\\=1\frac{2}{9}$$
Rewrite 2 as 18/9
18/9 - 7/9 = 11/9