Learn French: Elle fait de bonnes prédictions.

In French, when a plural adjective comes before a plural noun, the plural indefinite article des changes to de. Since the adjective bonnes comes before prédictions, we use de.

Would it be wrong to say des bonnes prédictions?

In strict, formal French, yes. The rule requires de before a preceding plural adjective. However, in casual, everyday spoken French, you will often hear native speakers say des bonnes prédictions. For exams or writing, always stick to de.

Why does the adjective bonnes come before the noun here?

Most French adjectives come after the noun. However, short, common adjectives that describe Beauty, Age, Goodness, or Size (often remembered by the acronym BAGS) go before the noun. Bonnes (good) falls into the 'Goodness' category, so it precedes prédictions.

Why does bonnes have an -es at the end?

Adjectives must match the gender and number of the noun they describe. The noun prédictions is feminine and plural. To match it, the masculine singular adjective bon doubles its 'n' to become feminine (bonne) and adds an 's' for the plural (bonnes).