Valid

Invalid

One Row

$(\text{p}\supset \text{q})\cdot (\text{r}\supset \text{s})$

$\text{p}\vee \text{r}$

$\therefore \text{q}\vee \text{s}$

$\text{p}\supset \text{q}$

~p

$\therefore$ ~q

Two Rows

$\text{p}\equiv \text{q}$

$\therefore (\text{p}\supset \text{q})\cdot (\text{q}\supset \text{p})$

$(\text{p}\supset \text{q})\vee (\text{q}\supset \text{p})$

$\therefore \text{p}\equiv \text{q}$

Three Rows

$(\text{p}\cdot \text{q})\vee (\text{p}\cdot \text{r})$

$\therefore \text{p}\cdot \text{(q}\vee \text{r)}$

$\text{p}\vee \text{q}$

$\therefore \text{p}\cdot \text{q}$