Emanuel M. answered 08/10/14
Tutor
New to Wyzant
Highly training honor student with a passion for academic success
x+-6=9 you want to leave x by its self and in order to do this you need to do the opposite operation of the number you are trying to bring over on both sides. in order words (-6+6=0) the six gets eliminated on the left side of the = sign.
you are left with x=9+6 which gives you x=15 when you add 9 and 6.
Remember what you do on one side you have to do to the other.