Now that's an interesting answer. Unfortunately the author didn't anticipate that response.

Please look at the problem you solved and compare it to this:

Check to see if you have exactly the same problem written down; perhaps you changed something (like one of the operation signs or a number). Check to see that the parentheses were properly placed.

If you found no copying error, double-check your arithmetic. Also, check to see if you brought down the correct quantities line-by-line, and be sure you didn't 're-use' any of them.

Now, make a NEW copy of the problem (be certain that you have this problem written down), then solve it carefully: