So the sum of her exam scores is 308. We can set up an equation where x=the overall grade she needs for her average to be a 68. x/5=68. This equation essentially is saying that the overall score she gets/5 which is the amount of tests she takes equals 68, her average. We multiply 5 on both sides and get 5x=340. Her overall score so far is 308, so we subtract the two and get 32, which is the grade she needs in order for her average to be a 68