In mathematics, a variable is a symbol used for a number not yet known, while a constant is a number or symbol that has a fixed value. The value of a variable can change depending on the equation, while the value of a constant always remains the same.

In the equation 5x - 3 = 7, x is the variable, as it represents a number with an unknown value. The constants in the equation are 3 and 7, because their values remain the same no matter how the equation may be altered. The number 5 acts a coefficient for the variable x, as x is being multiplied by 5.