Your question isn't clear. Unfortunately repeating it hasn't made it any clearer.
Perhaps you could give some idea of where you found the question and what the context of the question is. The question doesn't state what you're trying to estimate. Is there a picture or diagram? Is it algebra, geometry, arithmetic, ...? Maybe a photo of the question from a book would help. You can upload photos using the menu facility (image) next to table (hover the cursor over the icons). This facility allows you to upload from your photo files.
EXAMPLE
16 estimated by 9 could be an estimate of 16 divided by 9. Since two nines make 18 an estimate of 16 divided by 9 would be (about) 2 because two eights make 16 and 8 is close to 9.