Answer:
A. 22
Explanation:
You want an estimate of the difference between 28 5/12 and 6 7/15.
Approximation
The two numbers can be approximated (to the nearest half) by 28 1/2 and 6 1/2. Their difference is then ...
28 1/2 -6 1/2 = (28 -6) +(1/2 -1/2) = 22
The estimated difference is ...
A. 22
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Additional comment
The actual difference is ...
(28 5/12) -(6 7/15) = (28 -6) +(5/12 -7/15) = 22 +((75 -84)/180) = 22 -1/20
= 21 19/20
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