3x+8<2, 3x<-6, x<-2; or x+12>2-x, 2x>-10, x>-5. So x<-2 OR x>-5 (but not both). If x<-2, x≤-5 because it cannot also be >-5; or if x>-5, x≥-2 because it cannot also be <-2. In the (exclusively implied) OR case, x must satisfy one of the inequalities, and it must not satisfy the other. EXAMPLE: x=-5 satisfies x<-2, because -5<-2, but x>-5 does not x=-5. x=-6 would also satisfy x<-2 while not satisfying x>-5, because -6<-5. Similarly x=-2 satisfies x>-5 but does not satisfy x<-2. If x=0, x>-5 but x≮-2 (same as x≥-2).
Compare OR above with the AND situation where both inequalities have to be satisfied.
If x<-2 AND x>-5 then -5<x<-2 (x is between -5 and -2 exclusively).