In order for the Destroyer to be fully efficient you shoudl not only go through it a few times but you should comprehend and be verse with the explanations that are offerred. The explanations are the key. Make sure you know them thoroughly and the test should be a breeze. Thats what i did at elast and my sciences came out to be
Organic: 25
Gen Chem: 25
Bio: 20
So definitely put as much time into it as possible and you will be satisfied with your results! Good luck to you!