The derivative of a difference is equal to the difference of the derivatives. We've seen that property. Or she could have said the derivative, she could have said this is equal to the derivative of seven plus the derivative with respect to x of negative five x. These two things would have been equivalent to this one. But for this one, she somehow forgot to include the negative. So I think she had a problem right at step one. Now if you just follow her logic after step one, let's see if she makes any more mistakes.