Pay down mortgage by selling Property #2 without capital gains?

[Chad R.]

Hello All,

My wife had her own house when we met, we live in the house I owned. She has been renting her place out since 2014.

If we sell her place can we use her equity to pay down the mortgage on the house we live in without having to pay capital gains?

Her details:

Original purchase $190K

Upgrades (to finish 2nd floor/ windows flooring etc) $22k

Approx Value $300k

Her Mortgage balance $110k

We have been looking into options of combining equity, initially to build but not sure if the scenario above is possible. More details available if required. 

Thanks