translate sentences into logic

Question

If I would like to translate the English sentence below into a predicate logic formula

"The parents of a green dragon are green"

Using predicates dragon, childOf and green, how would I go about this?

I understand that it may help to work the sentence into something that looks like logic, but I am getting stuck at how to represent "parents" as it is not a predicate.

Do either of these translations help me? Are they correct interpretations of the original sentence?

If a dragon is the child of green parents then it is green. All dragons who are children of green parents are green.

∀(X) . dragon(X) ∧ childOf(X)  ...?

please help. thank you in advance

Answer 1

$$\forall x (\exists y (y \text{is a green dragon} \wedge y \text{ is child of } x) \rightarrow x\text{is a green dragon})$$

Answer 2

Being a parent is a relation. Let $D$ be the predicate of being a dragon, $G$ being the predicate of being green and $P$ being the "is a parent of" relation.

Then we have: $\forall x\forall y (G(x)\wedge D(x)\wedge P(y,x))\implies G(y)$

Answer 3

I would use the following English paraphrase, which seems (to me) equivalent to the given formulation:

"For all x and y, if x is a dragon and x is green and x is a child of y, then y is green."