Set Theory

[nycmath]

See attachment.

[Math Tutor]

Y − X means: start with Y and throw out anything that also appears in X.

Y = {a, b, c, d, e}

a is in X — remove it.
e is in X — remove it.
b, c, d are not in X — keep them.

Y − X = {b, c, d}

So the answer is C. (Note that i, o, u belong to X only, so they never enter Y − X.)

[nycmath]

Y − X means: start with Y and throw out anything that also appears in X.

Y = {a, b, c, d, e}

a is in X — remove it.
e is in X — remove it.
b, c, d are not in X — keep them.

Y − X = {b, c, d}

So the answer is C. (Note that i, o, u belong to X only, so they never enter Y − X.)

You know exactly how to attack the problems. Very good.