We give several bounds for sdepthS(I+J), sdepthS(I∩J),
sdepthS(S/(I+J)), sdepthS(S/(I∩J)), sdepthS(I:J) and
sdepthS(S/(I:J)) where I,J⊂S=K[x1,...,xn] are monomial ideals.
Also, we give several equivalent forms of Stanley Conjecture for I and S/I,
where I⊂S is a monomial ideal.