Not sure about your answer their Damager, this looks like a Groups question in sheep's clothing.
Mind you, I only clued in on that once I hit statement 1.
Total = G1 + G2 - both + neither
From Q we have: 100 = Y + 7Y - both + neither
Looks to me that we need both S1 & S2 to come to an answer, so D for me
(and just to check)
100 = Y + 7Y - 0.7Y + 27
73 = 7.3Y
Y = 10 percent
X = 70 percent
both = 7 percent
Which makes me feel better, because all GMAT math questions, even DS, seem to need to work out cleanly.