Welcome to Nemeth! In the division problem, put the minus sign under the division symbol. In your second example, omit the arrows. The action is described in the text that accompanies the problem. I don't usually explain the omission in a tn, but it would not be incorrect-- if you can keep it short and clear.
Should I extend the separation line by one cell to the left of the minus sign then? If so, the separation line will not be the same length as the separation line that is part of the division sign. If not, the separation line will not extend beyond the longest line by one cell.