3 of them are in the so called "habitable zone." This is an area around a star where a planet could be located and have water in a liquid state on its surface. Out of the seven, there's a very good chance that at least one of them, maybe even two, has liquid water on its surface. That alone doesn't make the planet inhabited though. Think of all the stuff that makes earth inhabited. The moon is of great size in proportion to its planet (Earth). The moon controls the tides, and probably played a major role in the formation of life, as well as its spreading from the sea to land. The gas giants - located behind us - keep major asteroid and comet impacts to a minimum. If we were constantly getting hammered, life wouldn't be this far evolved. These are just a few things that make Earth inhabited too.
WHAT "7 earth like planets"?
No one can tell that yet.
scientists believe they could be
No one knows how many earth like planets there are or could be ...
Totally unknown. They are Earthlike, in the same manner that Venus and Mars are considered earthlike.
Read this and find out for yourself: [ Arxiv.org Link ]
So in all likelyhood, no. The solar system has four Earth-sized planets (such distances Mercury, Venus, Earth and Mars are pretty much indistinguishible at from an Earth-like exoplanet), which means that size and distance are not sufficient indicators of habitability.
Nobody knows but probably not.
There is know way of knowing. Astronomers believe that they orbit in the "habitable zone" of a dwarf star so they believe that there is at least a chance that they could support life.