Could someone explain with answers pls ?

Is the following always true for sets A, B, and C? a) A intersection (B \ C) = (A intersection B) \ (A intersection C)? Are the following true? a) {{{a}}} subsetorequalto b) {{a, b}} subsetorequalto {{{a, b}}} c) {{a, b}} subsetorequalto {{a, b, c}} d) {{a, b}, {a, c}} subsetorequalto {{a, c}}, {b, c}, {a, b}}