What sign does not represent the empty set

The sum of two numbers is 86, and their difference is 20. find the two numbers

The graph of a function f(x)=(x+2)(x-4). which describes all of the values for which the graph is negative and increasing? all real values of x where x< -2 all real values of x where -2

Glenda makes an online purchase for picture frames for $12.95 each and formats of $5.89 each the site says it taxes paid by the customer or 6.5% of the total purchase price shipping charges are based on the