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Chunjuwu,
Dookie is right. let me try explaining..

I will try to sync with Dookie, to avoid any confusion, but will try to be elaborate. Here is the approach.

Let Y be the rose produce in 1980. Let X be the the roses in 1981. We have

(1)Y= 1.4X. Since we have two variables and one equation, we need one more equation relating to Y and X to solve. Hence 1 by itself is insufficient.

(2) X=Y+10. Again this question stem has two variables and one equation. So (2) by itself if insufficient.

combining both (1) and (2) we have two equations and two variables and we can find X and Y for sure. We can solve, but pls dont solve (as per the practice in approaching DS problems).