I have unidentical breast and i am 21. can this problem be solved without plastic surgery because it's so noticeable.

Yes, of course: Many women are asymmetric (as are men sometimes in their scrotum). With modern undergarments, you will look amazing in any top you choose. I'd seek a specialized fitting at a ladies shop specializing in women with histories of breast surgery.

Not permanently: Asymmetric breasts (and other body features) are common but if it is enough of a difference to be bothering you, plastic surgery would really be your only permanent solution. Speak with board certified plastic surgeons about surgical options (breast augmentation, breast lift, breast reduction, etc) so you know what, exactly, your options are if you elected to have plastic surgery.