Then we are going to do the opposite of dividing 7 from 9 which is multiplying 7 from 9. (on both sides)
It will leave us with - X + 9 = 21
Then we will do the opposite of adding 9 to X which is subtracting 9 from X. (also on both sides) ( whenever you do any adding or subtracting or multiplying or dividing on one side you have to do it on the other for the equation to be true)
