选择题
2015 AMC 8 Problem 18: Arithmetic Sequence Grid
Each row and each column in a 5 by 5 array is an arithmetic sequence with five terms. The top-left entry is 1, the top-right entry is 25, the bottom-left entry is 17, the bottom-right entry is 81, and the center square is labeled X. What is X?
2015 AMC 8 第 18 题：算术序列网格
5 x 5 数组中的每一行和每一列都是一个包含 5 项的算术数列。左上角的条目是 1，右上角的条目是 25，左下角的条目是 17，右下角的条目是 81，中心方块标记为 X。X 是什么
A.
21
B.
31
C.
36
D.
40
E.
42