When you buy a rank, the value of the rank you've bought will be deducted from the price of the rank you're gonna buy next counting it as an upgrade, it's a small discount but still, hope I helped :)
I used to experience math anxiety too when I was younger, just go to your doctor / therapist and talk to him about it, thats what I did and my anxiety slowly disappeared in around 3 weeks, hope it helps!!:mc_38-0: