Answer:

Yes, the calculations in A were reasonable because the difference is pretty close to 0.
Explanation:
For part A,
-estimate the fraction 10/12 using 1/2 as our benchmark
The lower range is 1/2 and the upper range is 1
The halfway point is:

Therefore, our range is 1/2 < 3/4 < 1
10/12 ≥ 3/4, we round up to 1
-estimate the fraction 3/8 using the 1/2 as our benchmark:
The lower range is 0 and the upper range is 1/2
The halfway point is:

Therefore, our range is 0 < 1/4 < 1/2
3/8 ≥ 1/4, we round up to 1/2

For part B, the denominators are 12 and 8, so the LCM would be;

Then, we make a common denominator and subtract the numerators

For part C, compute the difference between the two results from parts A and B:

Yes, the calculations in A were reasonable because the difference is pretty close to 0.