What is the estimate answer and the exact answer of 17/10 : 2 4/5

Both 17/10 and 2 4/5 should be rounded up in preparation for this estimation.

17/10 is close to 2 and 2 4/5 is close to 3. Thus, your estimated answer should be

2/3, or approx. 0.6666 ...

Exact answer: divide 17/10 by 14/5. LCD is 10, so convert 14/5 to 28/10.

Now divide 17/10 by 28/10. Answer: 17/28 = approx. = 0.607 approx.

These two results are comparable: 0.6666 ... and 0.6071 ...