Question 25485
Consider the arithmetic of this statement:
  2<7
Now multiply both sides by (-1)
If you did not switch the inequality sign you
would get -2<-7
But that is not true:
You must switch the inequality sign to get -2>-7

Or consider 2<-3y
Let's say you want to solve for "y"
Add 3y to both sides to get 3y+2<0
Now subtract "2" from both sides to get 
3y<-2
You started with 2<-3y
and ended with 3y<-2
See how the inequality has switched.

Cheers,
Stan H.