If we earn money by solving exams of others or doing assignment of others then the money we earn by this is halal or haram?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu`alayhi wa sallam, is His slave and Messenger.

The intent of homework is to motivate students to study, just as the intent of tests is to determine the level of the student. Whoever solves the homework or assignment that the student is asked and supposed to do on his own, or answers them in the test, has helped him to cheat and lie to his teachers, and whoever takes money from him in return for that forbidden help, his money is evil earning that is Haraam.

Allah knows best.