Question: I want to say the phrase "I can understand about 60% of the content of this video" in japanese. I translated it to:

このビデオの内容は６０％ぐらい分かれます。

Is this correct?

Answer: 
First off your attempt:

> 
> このビデオの内容は６０％ぐらい分かれます。
> 
> 
> 

This attempt is incorrect but probably comprehensible to your listener. First, there is no possibility conjugation of 分かる or if you prefer 分かる like 入る already includes the normal sense of possibility in it.

Second, let's think about the aspect you're stating this in. 60% means that you're either measuring how much you believe you've understood (in the past) or you're estimating it in an ongoing fashion.

Third, stating 60% by itself might sound a bit overly-precise, so it seems wise to use a couching expression (ぼかし表現) to make this a bit softer.

So I might suggest:

> 
> このビデオは６割ぐらいわかりました。
> 
> 
> 

= I understood about 60% of the video.

or

> 
> このビデオの内容はほぼ６０％理解できる。
> 
> 
> 

= I am able to understand about 60% of the video's contents.
分かれる is an intransitive verb meaning "to split or divide." The verb わかる (usually written without the kanji) encompasses the meaning "able to understand." If you want to emphasize "can comprehend," you can use the Sino-Japanese word and say 理解できる。Keep in mind that 理解する, unlike わかる, is a transitive verb, although this is irrelevant in your sentence because the object is topicalized. There are also some nuances in meaning and formality differences between 理解 and わかる that you can read about, e.g., [here](https://www.italki.com/question/156645).