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