okay each of you Asus Monitors have 2xHDMI 1xvga 1xearphone jack and 1 pc audio in
as per web page https://www.asus.com/us/Monitors/MX279H/
and rear of monitor image below:
your using a dual 980TI in SLI, which makes the ports on the second card turned off, and gives it processing power to the first video card (that is basically how sli works), so in SLI mode, you have to connect your monitors to the first video card
1xHDMI to Monitor 1, and;
1xDVID (M) to HDMI (F) converter and 1xHDMI cable to second monitor
ie:
http://www.microcenter.com/product/357496/DVI-D_Male_to_HDMI_Female_Adapter
plug that into the DVID connector of video card, plug HDMI to it and into monitor.,
your done!