First you must combine like terms, the two terms I this expression are x, and xy. So by adding -2xy to -2xy you get -4xy. Next you must add 3x to 3x. This gives you the simplified expression -4xy+6x. Hope this helps
For both lines the slope is 5/2 or 2.5.
Since the y-intercept is zero for both, both the equations are:
y=2.5x
Or
y=5/2x
What are we supposed to be basing this off of? is there no additional information?