Estimate the difference by rounding each number to 0, 1/2, or 1 before subtracting.
7/8-7/9
Rounding 7/8 to 1 and 7/9 to 1 gives:
1 - 1/1 = 0
Therefore, the estimated difference is 0.
7/8-7/9
1 - 1/1 = 0
Therefore, the estimated difference is 0.