An inlet pipe can fill an empty pool in 3 hours. Another pipe can fill the same pool in 4 hours. How long will it take to fill the pool if both pipes are on?

time=1pool/(1pool/3 + 1pool/4)

Notice the rates add..1pool/4hrs + 1pool/3hrs.

time=12/7 hrs

so would this be 7 hrs or do i need to divide it out?

You didn't work it out at all, just copied my outline. Work it out to get the answer, then you will answer your own question. This is a nice exercise in fractions.