Just do it anyway. Not exactly to every single trivial step like simple arithmetic calculations, but just make sure your marker can follow it. I get told off for "lack of working"
hmm your offline now but it is best to show all working out. As if you get the answer wrong but show some working out you are bound to get some marks but with no working out and a wrong answer there isn't much that can be done.
I hope you did well in your exam, enjoy the rest of year 10.
It sucks when you lose marks solely for not showing working out. So, yes, for maths, look at how many marks the question is worth, and show working out according to that.