 Have you ever been frustrated using a Texas Instruments Calculator when you type an expression wrong and you feel like you have to start all over again? Watch this video. Here's three ways to edit any expression plugged into any Texas Instruments Calculator that has an equation-based operating system. To delete a character that you no longer want in your expression, use the left and right arrows to scroll to that character. When it's highlighted, press the DEL button and it will be erased. To overwrite a character in an expression with a different character, scroll over until that character is highlighted and select the character you'd like to replace it with. To insert a character at the beginning or the middle of an expression, go to the position just after where you would like to insert the character so that it is highlighted, press second and then delete. Note the highlight characteristics change to an underscore and press the character you'd like to insert just before this position.