Viewing defined variables
To view all the defined variables you have entered, go to the "Variables" tab, where you can scroll through the variables. If you tap on a variable, it will insert it into the equation box in the Keypad view.
To define a variable, you must manually edit the equation. To do this, tap and hold on the equation box in the "Keypad" tab. When the keyboard comes up, type the name of the variable you wish to define followed by an equals sign, then type the equation. An example would be a=3+4 . When you are finished, hit the "Done" button on the keyboard, and then tap the "=" button on the keypad to define the variable. Note that if you don't assign a variable, PEMDAS automatically assigns the result of that equation a unique variable name, such as ans23. The result of the last calculation is always stored in the "ans" variable.
Inserting variables into the equation
To insert a variable into the equation, first go to the "Variables" tab and locate the variable you want to insert. Then tap that variable, and PEMDAS will bring you back to the Keypad view and insert the variable into the equation.