Equations and Expressions Crossword

An expression doesn’t have this.
A letter that stands for an unknown value.
A number on it’s own in an equation
A number used to multiply a variable
When you combine all the like terms in an expression
Opposite operations that undo each other
A combination of numbers and operation symbols
The order which numbers are added or multiplied don’t change the sum or product
The rule which tells which operation goes first
Parts of an expression that are separated by addition and subtraction signs