Has this question been officially solved? IMO, the answer is E.
Algebra
Let's assume portfolio value is P, X% increase, Y% increase, Z% decrease
From 1985 -> 1990 the value went from P ---> P*(1+(x/100))
From 1990 -> 1995 the value went from P*(1+(x/100)) ---> P*(1+(x/100))*(1+(y/100))
From 1995 -> ???? the value went from P*(1+(x/100))*(1+(y/100)) ---> P*(1+(x/100))*(1+(y/100))*(1-z/100))
Target question asks: is P*(1+(x/100))*(1+(y/100))*(1-z/100)) > P ?
Divide by P on both sides: is (1+(x/100))*(1+(y/100))*(1-z/100)) > 1 ?
You could keep working with the algebra to simplify if you feel comfortable, but the math can get tricky if you're trying to keep it under 2 minutes. I would suggest looking at the equation above and testing MAXIMUM numbers and visualize/approximate to keep it around 2 minutes.
STATEMENT 1
X + Y > Z
Case A: make these far apart: X=Y=100 and Z=1. If you start at $100, you double to $200, then double to $400, and take a small hit (1%) and up around ~$400 > $100. Target answer: YES
Case B: make these close together X=Y=100 and Z=199. If you start at $100, you double to $200, then double to $400, and then take a massive hit (199%) and end up negative ~(-$400) < $100. Target answer: NO
Two different target answers INSUFFICIENT
STATEMENT 2
Y - X > Z
Personally, I would rearrange to Y > X + Z but that's personal preference.
Case A: make these far apart: Y=100 and X=Z=1. If you start at $100, add 1% and then double it you're at $202 and take a small hit (1%) you end up ~$200 > $100. Target answer: YES
Case B: make these close together X=1, Y=100, Z=98. If you start at $100, add 1% and then double it you're at $202 and take a massive hit (98%) you end up slightly more than ~$0 < $100. Target answer: NO
Two different target answers INSUFFICIENT
STATEMENTS 1 & 2
Combining X + Y + Y - X > Z + Z reduces to 2Y > 2Z so Y > Z and X does not matter. Since X does not matter, let's just set it to 0 so that we know 1980=1985 and there is no change at first.
Case A: make these far apart: Y=100 and Z=1. If you start at $100 and then double it you're at $200 and take a small hit (1%) you end up ~$200 > $100. Target answer: YES
Case B: make these close together Y=100 and Z=99. If you start at $100 and then double it you're at $200 and take a massive hit (99%) you end up ~$0 < $100. Target answer: NO
Two different target answers INSUFFICIENT
Therefore, both statements together are INSUFFICIENT, I would choose E.
Those calculations would probably take more than 2 minutes, but you get the idea of choosing extremes (1%, 99%, 100%) and then approximating them.
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