If I purchased a Vehicle for biz but used a personal vehicle for trade in how do use the 179 deduction?

I purchased a Ford F150 in 2017 for approx. 80% use for my biz. Price was 48k but used a personal vehicle for trade in and also put cash down payment. Purchase price for new vehicle is 48k......personal trade 16k.....down payment 9k.  Financed amount is 23k plus TTT.  How do I apply this to 179?