# Is an algebra of measure a sigma algebra

Given a sigma algebra $$mathcal {F}$$ on a tray $$X$$. Let's be even more sigma ideal $$I$$ https://en.wikipedia.org/wiki/Sigma-ideal. Then we can consider $$mathcal {F} / I = {[A] mid A in mathcal {F} }$$ or $$[A] = {A triangle Z mid Z in mathcal {F} }$$.

is $$mathcal {F} / I$$ still a sigma algebra? And a sigma algebra on which set, on [X]?