Calculator

Who remembers this from school?
There was a girl who was 13. (Type 13)
She had a bra size 84. (Type 84)
But she wanted size 45. (Type 45)
She went to the doctor. "Oh", said the doctor. (Type 0)
Take the pills 2 times a day. (Type 2x)
But she took them 4 times a day. (Type 4)
Which made her. (Type =)
Now turn the calculator upside down.
(If you've used Windows calculator, you'll struggle at this point.)