Why does the inequality sign flip when dividing by a negative?

This makes sure the eniquality stays the same.

ill give an example

if we did not flip the sign it would look like this 
-7x> 98
x>98

in this case lets plug in 100.
-7(100)>98
-700>98
because we did not flip the sign the inequality is wrong. 

Ill show you the proper way,  -7x>98
x<-14

so we can plug in any number that is less than -14, lets use -100.
-7(-100)>98
700>98, now the inequality is true

Perimeter of a rectangle =L+L+B+B
6+6+2B=34
12+2B=34
B=11