first lets solve for x
9x-7y=-7
it will be easier to start if the equation is equal to 0
so first add 7 on both sides
9x-7y=-7
+7 +7
now we have
9x-7y+7=0
now to get x on one side subtract 9x from both sides
9x-7y+7=0
-9x -9x
--------------------
-7y+7=-9x
now to get x alone we divide both sides by -9
7/9y-7/9=x