Please reply with Qur'An And Sahih-Hadith.
“Allahumma infa’nii bimaa ‘allamtanii wa’allimnii maa yanfa’uunii. Allahumma inii as’aluka fahmal-nabiyyen wa hifzal mursaleen al-muqarrabeen. Allahumma ijal leesanee ‘aiman bi dhikrika wa qalbi bi khashyatika. Innaka ‘ala ma-tasha’u qadeer wa anta hasbun-allahu wa na’mal wakeel.”
“Oh Allah! Make useful for me what you have taught me and teach me knowledge that will be useful to me. Oh Allah! I ask you for the understanding of the prophets and the memory of the messengers, and those nearest to you. Oh Allah! Make my tongue full of your remembrance and my heart with consciousness of you. Oh Allah! You do whatever you wish, and you are my availer and protector and best of aid.”
“Allahumma inni astaodeeka ma qara’tu wama hafaz-tu. Farudduhu ‘allaya inda hajati elahi. Innaka ‘ala ma-tasha’-u qadeer wa anta hasbeeya wa na’mal wakeel”
“Oh Allah! I entrust you with what I have read and I have studied. Oh Allah! Bring it back to me when I am in need of it. Oh Allah! You do whatever you wish, you are my availer and protector and the best of aid.”
The Prophet (sallallaahu `alayhi wa sallam) told the following dua to be recited in stress, studies, exams and trials
"Allahumma la sahla illa ma ja'altahu sahla wa 'anta taj-alul hazna idha shi'ta sahla"
“O Allaah, there is no ease except what You make easy. And if You wish, You make the difficult easy.” [recorded in Hisnul-Muslim]
Must read dua for exams( especially for written exams).