Du'a to succeed in exams

فَإِنَّ حَسۡبَكَ ٱللَّهُۚ هُوَ ٱلَّذِيٓ أَيَّدَكَ بِنَصۡرِهِۦ وَبِٱلۡمُؤۡمِنِينَ

Fa-inna hasbakallaah, Huwal-ladhee ayyadaka bi-nasrihee wa bil-mu'mineen

then lo! Allah is Sufficient for thee. He it is Who supporteth thee with His help and with the believers

Qur'an 8:62 (Al-Anfal)