To write the unit in acres per day. We have 2/3 acres and 7/8 days:
[tex]\frac{\frac{2}{3}}{\frac{7}{8}}\frac{\text{ acres}}{\text{ days}}=\frac{2\times8}{3\times7}\frac{\text{ acres}}{\text{ days}}=\frac{16}{21}\frac{\text{ acres}}{\text{days}}[/tex]Answer: 16/21 acres per day