If the number is x then 2x+6<-16. Divide through by 2: x+3<-8, and subtract 3 from each side: x<-11. So all numbers less than -11 make this inequality true. Example: x=-12: -24+6=-18 which is less than -16 TRUE. But x=-11: -22+6=-16 which isn't less than -16 FALSE, as expected.