What is a suitable rewrite of "He can solve complex math problems" using "to be able to"?

The correct rewriting of "He can solve complex math problems" using "to be able to" is "He is able to solve complex math problems." This transformation accurately captures the original meaning of the sentence, which indicates the subject's capability or proficiency in solving complex math problems.

The phrase "is able to" effectively conveys the ability in the present tense, similar to "can." It suggests that he possesses the skills required to tackle these problems without implying any time frame or specific instance.

Other alternatives do not maintain the original meaning as effectively. For instance, stating that "he is solving" changes the focus to an ongoing action rather than a general ability. Similarly, "he has been able to" suggests a past experience of being capable, but it does not directly affirm his current ability. Lastly, "he will solve" implies a future intention rather than expressing current capability, which diverts from the original sentence's intent.