The key with math is repetition. With Destroyer you have what? 10, 12 tests that you can practice with?
Time yourself, 45 minutes, answer as quickly as you can on each. If you can't answer, go past it, come back. But make sure you have given each question its allotted time.
When you are done, go through it. Yes, you will miss questions and possibly because you were rushed. The key here is to synthesize what you are doing wrong. Now is the time to correct and get faster. And to learn what you don't know.
Again, Destroyer isn't the test. This is practice and you should practice under real conditions. Get yourself laminated sheets, dry erase marker and eraser. Time yourself in EVERYTHING, and see what needs improving.
My QR is not that hot. 18. But This is up from a diagnostic of 14 and my prometric experience was horrible. I had to get up and get my sheets replaced because they told me I was not allowed to erase. That I had to turn in marked pages and get new ones. But I assure you I did not run out of time and every question was answered.
If I had not trained under test conditions I would have done worse.