Regettably, "dyslexia" is used by many people who do not have the condition to excuse their lack of expertise with words. I expect many others will blame some sort of condition for not knowing how to do maths. I can do all sorts of mental arithmetic, not because I am clever, but because I was made to do it by my parents and my teachers who would probably be locked up now if they used the methods they used on me. It was normal to test times tables every morning and the headmistress used to come in the classroom without notice, get a child to stand in front of the class and recite a given table. Ridicule and cane often followed.
I can, however, take comfort in the fact that I can add up my supermarket shopping as I go round and have the exact money in my hand when asked. The look on the till assistant's face is often a picture. I take the view that anyone who respects themselves and their future prospects could practice arithmetic, which can be done very easily every day. After all, I have seen uneducated farm workers take 39 away from 472 in a flash when playing darts. I guess I am in the minority by not wanting to use a calculator.