"Estos platos son muy grandes."
Translation:These plates are very big.
I chose 'these are very big plates' the word order is different but dl users seem to say that translations are not word for word so why is my answer wrong?
"Word for word" is something different. In general, you should stay close to the word order of the original sentence when translating.
Specifically, you moved the "plates" from the subject position to the object position. So instead of talking about what size these plates are, you now talk about what "these" are. Your sentence would be translated as "Estos son platos muy grandes."
This is one thing 'they' play with: "plato" has two concepts 1: a plate (that is small or big) 2: a dish that is put on the plate ( which can be grand or less). No problem with that, unless they are not stuffed one after another in sequence, as DL often does.