Question 1006156
I'm not sure what you mean by "box"


Here is how I'd do the proof


<table border=1><tr><th>Number</th><th>Statement</th><th>Lines Used</th><th>Reason</th></tr><tr><td>1</td><td>H =&gt; J</td><td></td><td></td></tr><tr><td>:.</td><td>~J =&gt; ~H</td><td></td><td></td></tr><tr><td>2</td><td>~H v J</td><td>1</td><td>Material Implication</td></tr><tr><td>3</td><td>J v ~H</td><td>2</td><td>Commutation</td></tr><tr><td>4</td><td>~~J v ~H</td><td>3</td><td>Double Negation</td></tr><tr><td>5</td><td>~J =&gt; ~H</td><td>4</td><td>Material Implication</td></tr></table>