How can I ask for help in an adult maths class without feeling as though I'm holding everyone back?

I knew the recipe said three quarters of a cup. When the worksheet asked for a different batch size, I wrote a number, crossed it out, and waited for the tutor to put the answer on the board.

I'm forty-eight and taking an evening numeracy class before applying for a course next year. In the first lesson the tutor said, "This is probably a quick recap for most of you." I laughed with everyone else. It wasn't a recap for me.

Now I copy the worked answers neatly enough that my page looks finished. The tutor can't see where I got lost. I want to ask about the step between the two lines, but I imagine the rest of the room waiting while I admit I never understood it.

Would it be better to speak after class, send the unfinished attempt, or ask during the example? I enrolled to learn this. At the moment I'm learning how to make my notebook look reassuring.