Verified Answer :

9 - 4x = 57
first u would take away 9 on both sides 
9-9 - 4x = 57 -9 
-4x = 48
then u would divide 4 on both sides
-4x/4 = 48/4
-x = 12
so if negative x (-x) is 12 then positive x will be -12 
x = - 12 is ur answer