The cell should look like this:

See, there is no tf.subtract() before the “### YOU CANNOT EDIT THIS CELL”. If you cannot edit it, try getting a clean copy of your assignment as instructed here.
The cell should look like this:

See, there is no tf.subtract() before the “### YOU CANNOT EDIT THIS CELL”. If you cannot edit it, try getting a clean copy of your assignment as instructed here.