I just got Jsou veliké and Jsou veliká towards....Now i am tryna to find difference(which one is used for(masculine and etc.))
I suggest reading the provided tips and notes sections that are accesible on Duolingo web version.
Masculine is probably velike, velika is feminine? If that's what you are asking
As it is plural, it is not feminine, it is neuter: singular veliké, plural veliká.
Given that it is plural neuter, would you ask this of a group of boys and girls together? Or would you ask this about a group of things? Thanks!