求助几道GWD数学题，帮我解答一下，谢谢！！！

For all integers x and y, the operation D is defined by xDy = (x+2)² + (y+3)².  What is the value of integer t?

(1)     t D 2 = 74

(2)     2 D t = 80

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

本题答案是C,但我认为是E，因为t的值是不确定的

A.   55%

B.   20%

C.   25%

D.      30%

E.       35%

本题也是不明白题意，绕来绕去的，能帮我分析一下题意吗？谢谢！答案是C

What is the greatest common factor of the positive integers j and k?

(1)     k = j + 1

(2)     jk is divisible by 5.

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.

本题一点思路都没有，希望指点一下！谢谢！答案是A

One kilogram of a certain coffee blend consists of x kilogram of type I coffee and y kilogram of type II coffee.  The cost of the blend is C dollars per kilogram, where C = 6.5x + 8.5y.  Is x < 0.8?

(1)     y > 0.15

(2)     C ≥ 7.30

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.

像这样的题，我总是搞不定，希望帮我分析一下！答案是B

是不是有点多？回答一个也好，急切等待分析，谢谢！