This is the 89th most frequent Indonesian word.
memang
Certainly; indeed; admittedly.
Here, 'memang' is used to confirm something considered true or obvious, adding emphasis to the statement that the person is clever in mathematics.
Dia memang pintar dalam matematika.
He indeed is clever in mathematics.
In this sentence, 'memang' is used at the beginning to introduce confirmation or agreement with the sentiment about the decision being wise.
Memang, keputusannya sangat bijaksana.
Indeed, his decision is very wise.
Here, 'memang' is applied to acknowledge a fact or truth about the speaker's intentions, while also connecting it to a subsequent contrasting statement.