Rearrange the parts of the sentence in the correct order.
Public goods are
P-important as they
Q-mitigate the impact of
R-income poverty and inequality

Let's evaluate the parts:
"Public goods are" is a linking construction requiring a predicate adjective or descriptor. Part P ("important as they") seamlessly continues this.

The pronoun "they" in part P requires a plural verb, which is fulfilled by Q ("mitigate the impact of").

The prepositional phrase ending with "of" in part Q requires an object, which is provided by R ("income poverty and inequality").

Hence, the sequential order is PQR.