What following statements contain a variable?

A statement contains a variable if it includes a symbol or letter that represents an unknown value. For example, in the equation ( x + 5 = 10 ), the letter ( x ) is a variable. Similarly, in a function like ( f(t) = t^2 + 3 ), the ( t ) is a variable. In contrast, a statement with only constants, like ( 3 + 5 = 8 ), does not contain a variable.