Joanne invited 21 friends to her party. Some of her friends couldn't
attend. She ended up having 16
friends at the party. How many
friends couldn't go to the party?

Mary works for a company that ships packages and must measure the size of each box that needs to be shipped. mary measures a box and finds the length is 7 inches, the width is 14 inches, and the height is 15 inches. what is the volume of the box? [type your answer as a number.]

Need asap. solve for the following inequality

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?