求教三道GWD数学题

Maggie草

1.
if X>1 and Y>1, is X<Y?
   (1) X^2/(XY+X)<1
   (2) XY/Y^2-Y<1

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient

lStatement (2) ALONE is sufficient, but statement (1) alone is not sufficient

lBOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

lEACH statement ALONE is sufficient

Statements (1) and (2) TOGETHER are NOT sufficient

这题为什么是E呢，我怎么觉得是B呀

2. Last year in a group of 30 businesses, 21 reported a net profit and
15 had investments in foreign markets. How many of the businesses
did not report a net profit nor invest in foreign markets last year?
(1) last year 12 of the 30 businesses
reported a net profit and had invest-
ments in foreign markets.
(2) last year 24 of the 30 businesses
reported a net profit or invested in
foreign markets, or both.

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient

lStatement (2) ALONE is sufficient, but statement (1) alone is not sufficient

lBOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

lEACH statement ALONE is sufficient

Statements (1) and (2) TOGETHER are NOT sufficient

这道题貌似之前也讨论过，但是我还是想要一个比较明确的答案，为什么是B，不是D呢

3.
If the average (arithmetic mean) of the assessed values
of x houses is $212,000 and the average of the assessed
values of y other houses is $194,000, what is the average
of the assessed values of the x+y houses?

(1)x+y=36
(2)x=2y



A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

这一题我觉得B就完全可以了呀，为什么是C呢

请NN们帮帮忙吧