Variable: In mathematics, a variable is a symbol used to represent an unknown value or quantity. It can change or vary in different situations or equations.
Expression: An expression is a combination of numbers, variables, and mathematical operations without an equal sign. It represents a value but does not state any relationship between two quantities.
Solving: Solving refers to finding the values of variables that satisfy an equation or system of equations. It involves applying various techniques and operations until the unknowns are determined.