IMHO, trick question. The resolution of the three images is the same, which is therefore true. They are all the same pixel width and height.
On the other hand, the quality of the images are indeed different. Resolution does not equate to quality. The original image could have been scanned at 100, 300 and 600 dpi. Then all three images were reduced to the dimension sized used for the web page posting. The quality of the 600 dpi image would be better than the 100 dpi image.
As another example, take any TV Show, or movie, that has both a Blu-ray and DVD release, where the master video of the release is 1080p, or better (movies can be 2K or 4K mastered). The DVD release will have the resolution changed to 720x480, or 720x576 (depending on where it is released. Now take the DVD version and the Blu-ray version and play them on your Blu-ray player to you 1920x1080 HDTV. The DVD will look blurrier than the Blu-ray. That is because even though the resolution of the HDTV is 1920x1080, the DVD source being 720x480(576) is blown up to the 1920x1080 resolution. While the resolution displayed on the HDTV is the same, the quality of the image isn't. Displayed resolution vs. source resolution.
Going back to the three images, the 100 dpi image might have been enlarged to fit the pixel size for display, the 300 dpi might be 1:1 and the 600 dpi reduce to the pixel size used for display. The 100 dpi original would therefore look blurrier.
Some will say that it is all semantics. The question as asked about the three images that were posted, NOT what the resolution of the original sources were. Again, trick question.