If a= 2b, then a-c= 2b-c?? Which property of equality is being used?

Which of the following are parts of a sphere

Apublic library wants to place 4 magazines and 9 books on each display shelf. the expression 4s+9s represents the total number of items that will be displayed on s shelves. simplify the expression

What is always true about a positive integer raised to a negative odd power?