I passed both of my skills tests today for the first time trying and have discovered that the only way i was able to teach myself this maths was to just practice constantly! I only did practice papers really! Some tips i would give would be to know your times tables really well, understand mean, median, mode and range, and when doing the mental arithmetic, write down the numbers as the lady is reading them. I discovered that if you listen really well the first time, write down all the numbers they give you, and answer the question as the lady is reading it the second time, then you will have the 18 seconds to check you got it right! Obviously some you will struggle on and of course everyone does, but I found that after a week or so of practice, I was able to get most of them right! If you get 2 right out of the mental arithmetic, and get all of the other questions right in the rest of the test, then you will pass! Ive needed maths tuition for the past 8 years so if i can do it, you can too! I hope this helps and really good luck for them, they are quite nerve wracking but once you’re in there, you’re fine!