I've been trying to learn to expand expressions. I've found a particular tutorial with an example that I can't seem to understand, even though I know it's supposed to be very simple.

My understanding is that you multiply each term from within the brackets by the expression outside them. The example given is:

6g + 2g (3g + 7) = 6g + 2g x 3g + 2g x 7g (this is then simplified but that's not relevant to my question).

If 6g + 2g is the expression to multiply the bracketed terms by, then what's happening to the '6g' part when multiplying the '7'? Ie, how come it's not 6g + 2g x 3g + 6g + 2g x 7?

why does the '2g' get multiplied by both terms from within the brackets, but not '6g'?

I'd really appreciate it if anybody can explain what I'm getting wrong to me.

Thanks!