Passive to active

If you are using the word "perplexed as adjective, it is not possible.

BUT

The word "perplex" is used as a verb as well which means "to cause to be puzzled"

See: 

http://dictionary.reference.com/browse/perplexed?s=t

In this sense it can be converted into active voice, but for that a doer is required.

Her strange response perplexed me.

The purpose of education is to develop the quality of character. The process to develop character can be divided into three elements include, qualities personal, the power of thinking and knowledge and skills.