If the rectangle has a fixed width of 300, it means that

where
and
are width and length, respetively.
So given the length
, the are would be

1/5 of 200 is 40 which mean she gave 40 away and she has a 160 left
Given:
Steven wrote this equation:

To find:
The error in Steven's reasoning and then find the correct product.
Solution:
We have,

This statement is incorrect because we cannot write product directly as Steven wrote.
We need to multiply the place values of each digit of first number with the place values of second number and then we need to add the resulted values.




Therefore, the correct product is 72.