Inequality: An inequality compares two values, showing if one is less than, greater than, or simply not equal to another value.     

Variable: A Symbol for a value we don't know yet. It is usually a letter (e.g. x, y).  

Integer: A number with no fractional part (no decimals). (e.g. -16, -3, 0, 1, 198) 

Equation: A Mathematical statement that two things are equal 

Formula: A rule or fact written with mathematical symbols. (plural: Formulae)

Inverse operation: that undoes what was done by the previous operation (the opposite operation) 

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Command words:   

Rearrange: is to arrange the equation so that the unknown variable is by itself on one side of the equal signs.

Make 'a'  the subject of the formulae: rearranging the equation or formula so that we have a single variable (for example: a) equal to the rest of it. 

Substitute: replace one variable with a number or new variable. 

Solve: to find a value we can put in place of a variable that makes the equation true.  

Prove: to show that a statement is true in the context