Declension table of ?yathākartavya

Neuter	Singular	Dual	Plural
Nominative	yathākartavyam	yathākartavye	yathākartavyāni
Vocative	yathākartavya	yathākartavye	yathākartavyāni
Accusative	yathākartavyam	yathākartavye	yathākartavyāni
Instrumental	yathākartavyena	yathākartavyābhyām	yathākartavyaiḥ
Dative	yathākartavyāya	yathākartavyābhyām	yathākartavyebhyaḥ
Ablative	yathākartavyāt	yathākartavyābhyām	yathākartavyebhyaḥ
Genitive	yathākartavyasya	yathākartavyayoḥ	yathākartavyānām
Locative	yathākartavye	yathākartavyayoḥ	yathākartavyeṣu

Compound yathākartavya -

Adverb -yathākartavyam -yathākartavyāt