Can intelligence be inherited?

Partly. Intelligence is a combination of genetics and environment. It is the age old "nature vs nurture" controversy. Perhaps the best thing you can do for yourself is to participate in healthy, stimulating activites to broaden your mind.
0.7-0.8. Iq is widely found to be between 0.7 and 0.8 heritable which is fairly high for a human behavioral trait. But there is still a lot of room for environmental influence. It is very controversial subject, however. For a good overview of the arguments in favor of high heritabiliity, see "the bell curve" by murray. Heritability is not the same in all iq ranges.