Remember that parallel lines have the same slope.
y=3/7x+11 (in slope intercept form already)
-3x+7y=13 (standard form)
Add 3x to both sides, giving you 7y=3x+13, divide by 7 on both sides, giving
y=3/7x+13/7
Since both equations' slopes' are the same, their graphs will be parallel.