Learn Croatian: Kad bi savršena jednakost postojala, imali bismo pravednost. - If perfect equality existed, we would have justice.

They are created by adding the suffix -ost to the adjectives jednak (equal) and pravedan (just/fair). This suffix creates abstract feminine nouns, similar to "-ity" or "-ness" in English. Notice how the "fleeting a" in pravedan drops out to make pravednost rather than "pravedanost".

jednakost is the subject of the first clause, but pravednost is the object of the second. Why don't their endings change to show the case?

Nouns ending in -ost are feminine consonant-ending nouns (part of the i-declension). A key feature of this group is that their nominative and accusative singular forms are completely identical. So jednakost is in the nominative case, and pravednost is in the accusative case, but their dictionary form doesn't change.

Why does this sentence use kad bi for "if" instead of the more common word ako?

ako is used for realistic, possible conditions. Because the speaker is implying that perfect equality doesn't actually exist, this is a hypothetical or unreal scenario. Croatian expresses hypothetical conditions using kad followed by the conditional mood (bi + the l-participle, which in this sentence is postojala).

In the second clause, why is the word order imali bismo and not bismo imali?