Learn French: Quelle idée est créative et sérieuse ? - Which idea is creative and serious?

In French, adjectives must match the gender of the noun they describe. Idée (idea) is feminine, so the adjective must be too. For adjectives that end in -f in the masculine form (like créatif), you change the -f to -ve to make them feminine.

What is the masculine form of sérieuse?

The masculine form is sérieux. When a masculine adjective ends in -eux, you change the ending to -euse to make it feminine. Since we are still describing the feminine noun idée, we have to use sérieuse.

Why is it spelled Quelle instead of Quel?

Quel means "which" or "what," and it acts like an adjective, meaning it has to match the noun it belongs to. Because idée is feminine, you must use the feminine spelling, Quelle. If you were asking about a masculine noun, like a project (un projet), you would use Quel.

Why are the adjectives placed after the verb est here?