should I drop maths extension 1 (1 Viewer)

[Eagle Mum]

yea duh but im asking if they can take half a unit of a subject
e.g. they take eng adv, math adv, maths ext1, eng ext1, phys, eng ext 2 which is 9 units but i still have eco left
can they take 1 unit of eco if i performed the worst in that in all my subjects

Yes. They count two units of English plus eight of your best remaining units, and will split a two unit subject to make up the tenth unit. It’s been like this for decades.