The Casio MS 120TE is a 12-digit desk calculator that can perform basic mathematical functions such as addition, subtraction, multiplication and division. It is not equipped to handle algebraic, geometric or statistical problems. This calculator is suitable for school, home or office.

Push the purple "C/AC" button to turn on the Casio MS 120TE calculator on.

Enter the first number grouping in your equation. Enter the numbers from left to right. For example, if your equation is 123 + 456, press "1," "2" and "3" to enter the first grouping in the equation.

Push the button that correlates to the appropriate function: addition, subtraction, multiplication or division. For the sample equation of 123 + 456, press "+."

Enter the second number grouping in your equation. For the sample equation of 123 + 456, press "4," "5" and "6."

Continue entering numbers and functions until your entire equation is entered. For example, if the equation is 123 + 456 - 789 +321, push "-" followed by the next number of "7," "8" and "9" and continue on until the entire equation is entered. Once complete, press the "=," or equal button, to display the answer to the equation.