下列关于我国的描述，正确的是（ ）
已知小明的年龄是m岁，小红的年龄比小明的年龄的2倍少4岁，小华的年龄比小红的年龄的12还多1岁，求后年这三个年龄的和．
Judging from the message they convey, these two chapters are __________ independent of each other, that is, they are not in connection with the other at all.
