6y - 9 = 33
thing of the equal sign as a balance. everything on the left is currently balanced with everything on the right. So, we are going to work on isolating the y (getting it by itself) while keeping the equation balanced.
Start by 'undoing' addition/subtraction. in this case 'undo' -9 by adding 9 to both sides
6y - 9 + 9 = 33 + 9 (what you do to one side you do to the other)
combine like terms 6y = 42
then 6y means 6 times y so 'undo' multiplication by dividing (again both sides)
6y/6 = 42/6
6/6 = 1 so 1y = 7
the one is automatically implied and thus not necessary therefore answer is y=7