Translation:If he strived to learn, he would be a mathematics professor.
could be rather translates to olabilir because it indicates possibility.
On the other hand it's also a fact that we occasionally use olur instead olabilir. So their meanings are very close and they can be replaced with each other in this sentence. But still you should prefer the ending -AbIl when translating can/could.
In my neck of the woods, "If he had worked harder to learn, he would be a professor of mathematics." Yes, this is one of those times when a little adjustment would be helpful. It appears that there are many interpretations.
Oddly, while studying this, I realized--I think--how different "striven" is from "struggled". "Striven" appears to mean that he had made an effort to learn to his utmost. "Struggled", on the other hand, means--in my mind--that, even with his best effort, he might not have achieved his goal.
Is it for the past tense or present? Because I wrote: "If he strives to learn, He will be a mathematics professor". It accepted my answer and said: (Another correct solution: If he strived to learn, he would be a mathematics professor.) Wow, and How?
In addition, the hint for (için) gives (in order to) however it's not accepted here on Duolingo, I tested that.
Sorry but this translation has some problems .. turkish sentence is not in the past ..so it means that there is still a chance to be a professor we understand as turkish native speakers .. but the translation gives expression that there is no chance , it was in the past , he did not strived and missed the chance to be a professor , pitty .. and my answer was 'he would be a mathematics professor if he strived to learn ' should be accepted also .. and also at similar questions have been accepted like this .. same meaning ..