This may not have been clear enough. Adjective endings change based on the preceding article and the noun’s case and number, resulting in 3 \times 3 \times 2 \times 4 = 72 possible endings. Using rot (red) as an example, here’s the breakdown:
| No article Strong declension |
Masculine | Neuter | Feminine | Plural |
|---|---|---|---|---|
| Nominative | roter | rotes | rote | rote |
| Accusative | roten | rotes | rote | rote |
| Dative | rotem | rotem | roter | roten |
| Genitive | roten | roten | roter | roter |
| Definite article Weak declension |
Masculine | Neuter | Feminine | Plural |
|---|---|---|---|---|
| Nominative | der rote | das rote | die rote | die roten |
| Accusative | den roten | das rote | die rote | die roten |
| Dative | dem roten | dem roten | der roten | den roten |
| Genitive | des roten | des roten | der roten | der roten |
| Indefinite article Mixed declension |
Masculine | Neuter | Feminine | Plural |
|---|---|---|---|---|
| Nominative | ein roter | ein rotes | eine rote | keine rote |
| Accusative | einen roten | ein rotes | eine rote | keine roten |
| Dative | einem roten | einem roten | einer roten | keinen roten |
| Genitive | eines roten | eines roten | einer roten | keiner roten |
In reality, you only need to memorize the bolded endings. Mixed declension is indeed mixed, meaning memorizing strong declension is sufficient. The article changes are simpler, as these tables also demonstrate.