Find the two notches at the top of the calculator.

Insert a flat-head screwdriver into one of the notches and carefully pry open the top end of the case.

Locate where the case is still attached at the sides.

Insert the flat-head screwdriver into one side where the gap has widened.

Now gently pry apart the sides of the case.

Prying only one side will release the other side as well.