[typhoon2028]

An object placed in water will displace a volume of water equal to the volume of the object.

This is correct:
17-11.3=5.7 ml

1 ml = 1cm³

12.1g/5.7cm³ = 2.12g/cm³

The way you want to do it would give you a rock with a density lower than water.  I don't see many floating rocks!

[Borek]

12.1g/5.7cm³ = 2.12g/cm³

12.1g/5.7cm³ = 2.12g/cm³

What it is with you people, is it so hard to read forum rules? We don't give exact answers.

[JGK]

12.1g/5.7cm³ = 2.12g/cm³

12.1g/5.7cm³ = 2.12g/cm³

What it is with you people, is it so hard to read forum rules? We don't give exact answers.

Probably down to frustration BoreK; the OP seems to  have a rock like density and is incapable of recognizng help when given. Even spoon feeding the correct answer once didn't seem to take.

[typhoon2028]

I just copied an already posted answer.

My point was the poster should have logically figured out his density answer was incorrect.

[typhoon2028]

Also, not to be technical about rules, but I do not believe the answer is exact.  I believe the significant digits in the answer I posted are incorrect.

[408]

the OP seems to  have a rock like density

 

d=m/v

mass-you have
 volume- of the rock, which is equal to that of the water displaced.