First, I'd rewrite the original statement:
-2x > 3y
-x > 3/2 y
x < -3/2 y
Next, I'd rewrite what they give you for #2
2x + 5y - 20 = 0
x + 5/2y - 10 = 0
x = 10 - 5/2y
Now, take this x value and plug it into your rewritten equation from above
10 - 5/2 y < - 3/2y
10 < y
or
y > 10
so you know that y > 10. The question being asked is "is x negative"? You know that x has to be less than -3/2y (from the original statement). You can start picking numbers based on y > 10, (for example y = 11). When y = 11, x has to be less than -3/2 * 11, or less than -33/2. You can do the same for y = 12, 13, etc.
However, the easiest way to solve this is, since you already know that y > 0 is sufficient to solve the problem (from the first statement), then you know that y>10 also has to be sufficient, since y > 10 is included in the set "y > 0". Therefore, B is also sufficient.
(I didn't post the explanation to #1 since it seems like you already got that part)
my GMAT debrief:
https://www.beatthegmat.com/came-through ... 44327.html
You will not fear the terror of night, nor the arrow that flies by day,
nor the pestilence that stalks in the darkness, nor the plague that destroys at midday.
A thousand may fall at your side, ten thousand at your right, but it will not come near you.
- Psalm 91: 5-7
