Not sure if this is the right place for this...

On the Casio fx-991EX, I could type in a function, such as '2x+3', and after pressing the 'CALC' button, I could type in a value of x, and it would put it into the equation and give me the result. Does anyone know how to do this on a Casio CG50? I know I can just set a variable, and use that in the function, but the 991EX made it so much easier for doing this for multiple values.