Brainly has been the only thing keeping me from failing virtual, the answers there are mostly good, but occasionally you'll have a person who only give the answer. Which isn't very helpful for obvious reasons. The feature that prevents you from seeing more than a couple of answers each day is frustrating but it can easily be circumvented by using multiple free accounts. Overall I'd give it 5 stars if it weren't for the people who don't give explanations on their answers.