Suppose we made it this far into the proof and we were not quite sure what to do next.

We can always look at the aim box and the assumptions we've already made as a way to help us figure out what to do next. In this case, if we look at our current aim, that will prompt us for what to do on Line $3.$

What wff should we write in on Line $3,$ given our current aim?

$1(1)(($R & T$)->$ S$)$ A Aim:

$(($T $->$ R$)->($R $->$ S$))$

$($R $->$ S$)$

$2(2)($T $->$ R$)$ A$/$CP $($R $->$ S$)$

Remember $-$ Formatting will be important here! So$,$ enter your wff according to the following conventions:

Make sure you put no spaces between symbols.

Good Not Good!

Wffs: $($PvQ$)($ P v Q $),($P v Q$)$

Premises: $1,2,31,2,3$

Rules: $1,2$MP; $5$&E $1,2$ MP; $5$ &E

Use $\text{'}-\text{'}$ for the dash, a single minus sign.

Use $\text{'}$&$\text{'}$ for the ampersand.

Use $\text{'}$v$\text{'}$ for the wedge, a lower$-$case V$.$

Use $\text{'}->\text{'}$ for the arrow. Copy and paste the arrow from here, if you need it in your answer.

Use $\text{'}\text{'}$ for the contradiction symbol. Copy and paste the upside$-$down T from here.

Use $\text{'}\text{'}$ for the turnstile. Copy and paste it from here, if you need it in your answer.

Use $\text{'}$&I$\text{'},\text{'}$&E$\text{'},\text{'}$vI$\text{'},\text{'}$DN$\text{'},\text{'}$MP$\text{'},\text{'}$MT$\text{'},\text{'}$CP$\text{'},\text{'}$IP$\text{'},\text{'}$I$\text{'}$ for the rules.