Find the intersection of the sets. {a,b,c,d}∩∅

Find each sum or difference. -6 + (-13)

Multiply or divide as indicated. Write answers in lowest terms as needed. (3/20)∙(5/21)

Insert ∈ or ∉ in each blank to make the resulting statement true. 5 ____ {4, 6, 8, 10}

Find each sum or difference. -15+6

Simplify each exponential expression: $(-5x^3{y}^2)(-2x^{-11}{y}^{-2})$