The line given is -2x + 3y = 15, so we must rearrange:
=> 3y = 2x + 15
=> y = 2/3 x + 5
These two equations are EQUIVALENT, but one is in slope intercept form, the other isn't.
So in this case, gradient is 2/3 (or 2 units up, and 3 units across).
And we know that parallel lines have the same gradient. Hence, the general equation for lines parallel to it will be:
y = 2/3 x + n
where n can be any number (positive/negative, decimal/fraction/integer) except 5, which is original line.
For example, y = 2/3 x + 2
