what it wants you to do is to put it into a form where on the one side of the equation there is y and nothing else. for this, we need to get rid of the 0.9.
how do we do that?
we divide both sides of the equation by 0.9:
6.3/0.9=y
that's ugly, right? but if both denominator and nominator are decimal fractions of the same sort; we can multiply both by 10 and get rid of the point:
63/09=y
and...
so basically 7=y, or y=7
and this is the solution!