PP中的这几道题应该怎样做？

chailin1017

在做PP时不知道这种描述是什么意思，请大家指点
In the xy-coordinate plane, line l and line k intersect at the point (4,3). Is the product of their slopes negative?
(1) the product of the x-intercepts of line l and line k is positive
(2) the product of the y-intercepts of line l and line k is negative.

还有3个题，就是
If k is positive integer, what is the digit of the handred?
(1) the handreds digit of k+150 is 4
(2) the tens digit of k+25 is 7

If m is positive odd integer, 求 average of a certain set of the integers
(1) the integers in the set are consecutive multipels of 3
(2) the median of the set of integers is 3

最后一个是说两个水管注水的问题，单独cold- water leak 用C hours, hot-water leak uses H hours (the same container, respectively)，如果一起注水的话，用T小时。
其中有一个是 C/2 < T < h/2
这个是怎么推导出来的 ？

chailin1017

不知道该怎么理解！

自己先顶一下