diff --git a/docs/chapter_computational_complexity/time_complexity.md b/docs/chapter_computational_complexity/time_complexity.md
index a2cbaf20..7fc44030 100755
--- a/docs/chapter_computational_complexity/time_complexity.md
+++ b/docs/chapter_computational_complexity/time_complexity.md
@@ -186,7 +186,7 @@
     }
     ```
 
-根据以上方法，可以得到算法运行时间为 $6n + 12$ ns ：
+根据以上方法，可以得到算法运行时间为 $(6n + 12)$ ns ：
 
 $$
 1 + 1 + 10 + (1 + 5) \times n = 6n + 12