Parts of an Expression

A letter that represents an unknown number is called a _____.

What do you call each part of an expression that is separated by a $$+$$   or a $$-$$  ?

What is the coefficient in the expression: $$9a-12$$  ?

What is the coefficient of $$x$$  ?

$$8+5x-y$$  

What is the coefficient in this expression? $$3x+4-2$$  

In the expression $$4x-12$$ , what is $$4x$$  ?

How many terms are in the following expression?

$$7y+3+6k-9$$  

List the terms in this expression. $$7x-6+8$$

What is the coefficent in the following expression?

$$6-x+8$$  

How many terms are in the expression

$$3a+2b-c+10$$