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Yes, the strip of 3 stamps with selvage and plate number are Scott #279. Unfortunately, no one can tell from your scan if the stamps are mint (with gum) or without, which would greatly affect value. Assuming the #279's are mint with original gum, the 2011 Scott Catalog Value is $9 (mint) for each stamp. On the other hand, used values of that stamp are only 50 cents for each stamp. A small premium may be added for the plate number included on the selvage.
The 4-cent and 5-cent (blue) stamps shown in your second scan are Scott #280 and #281. Values for #280 are $25 (mint) and $3.25 (used); the 5-cent (blue) stamp is $32.50 (mint) and $2.25 (used).
The 5-cent (brown), 8-cent and 10-cent stamps shown are from an earlier series (note they don't have triangles in the upper corners). They would be 5-cent #223 at $80 (mint) and $4.50 (used); the 8-cent #225 at $60 (mint) and $17 (used); and 10-cent #226 at $190 (mint) and $4.25 (used).
The second row center (rose color) 3-cent stamp looks to be #65 valued at $3 (used); the bottom row (green color) 3-cent stamp looks to be #147 at $2 (used). (I qualify the term "looks to be" as there are a few varieties of these stamps that look similar but are worth considerably more, but we'd need a more detailed scan to identify those subtle varieties.)
Keep in mind that catalog values quoted are only a reference and the actual values on the re-sale level are likely to be only a small percentage of what the catalog lists as values. In stamps, condition is everything and some of your stamps appear to have minor faults (i.e. perforation pulls at the bottom right of the 4-cent stamp (#280); a fold or crease in the 3-cent green stamp (#147), etc.) which greatly diminishes the value. Also keep in mind that these stamps were issued in relatively high quantities and even though they may be old, they are still quite common in collector's hands so demand for them may be quite limited and would also affect value.
If you don't have a Scott Catalog, I suggest you acquire one, as it contains a wealth of information you will need to identify the stamps in your collection. If the price of a new catalog is not affordable, older copies are often available on
ebay or other auction sites, or you could even purchase a copy of the Postal Service Guide to US Stamps (available at your local post office) at $20. While not as detailed as the Scott catalog, the values are there, and so it serves as a good reference for a beginner collector.
Also, check with your local public library, as you may be able to borrow a Scott Catalog from their Reference Section.
Enjoy the stamps. It seems you have a very nice start to a good stamp collection!