In these problems, we want to get #x# all by itself on one side of the equation and everything else on the other side. That's when we can say we've solved for #x#. So, we'll start by moving the 9 to the left side of the equation by subtracting it from both sides:

#y = 5x+9#

#y-9 = 5x+9-9#

We can see that they cancel out, since #9-9 = 0#:

#y-9 = 5xcancel(+9-9)#

Now, all we have to do to get #x# by itself is to get rid of the 5 next to it. We do this by dividing by 5:

#y-9 = 5x#

#(y-9)/5 = (5x)/5#

Because #5/5 = 1#, the fives cancel:

#(y-9)/5 = cancel(5/5)x#

To finish, we state our solution:

#x = (y-9)/5#