This is the 582nd most frequent Chinese word.
简单
Simple; easy.
简单 in this sentence is used to describe the characteristic of the math problem, indicating that it's easy to solve.
这道数学题很简单。
This math problem is very simple.
简单 here describes the method used to resolve the issue, emphasizing straightforwardness or lack of complexity in approach.
他用一种简单的方法解决了问题。
He solved the problem using a simple method.
简单 in this context refers to an uncomplicated or minimalistic lifestyle, representing a philosophical or qualitative aspect of how life is lived.