9 5/21 - 10 2/3 - 3 5/28

To subtract mixed numbers, first convert them into improper fractions. Then, subtract the fractions and simplify if necessary. Finally, convert the result back into a mixed number if desired.

Let's begin:

9 5/21 = (9 * 21 + 5) / 21 = 193/21

10 2/3 = (10 * 3 + 2) / 3 = 32/3

3 5/28 = (3 * 28 + 5) / 28 = 89/28

Now, subtract the fractions:

193/21 - 32/3 - 89/28

To do this, we need a common denominator. The least common multiple of 21, 3, and 28 is 84.

193/21 = (193 * 4) / (21 * 4) = 772/84 32/3 = (32 * 28) / (3 * 28) = 896/84 89/28 = (89 * 3) / (28 * 3) = 267/84

Now, subtract the fractions:

772/84 - 896/84 - 267/84 = (772 - 896 - 267) / 84 = (772 - 1163) / 84 = -391/84

Since the resulting fraction is negative, we can write it as a negative mixed number:

-391/84 = -(391/84) = -4 23/84

Therefore, the result of the subtraction is -4 23/84.