Answer:
Pio and her sister can finish the dishes in 20 minutes if they work together.
Explanation:
Given that:
Pio can wash the dishes in 1 hour or 60 minutes
Her sister can wash the dishes in half hour or 30 minutes.
Let,
x be the time it would take for both of them.

Hence,
Pio and her sister can finish the dishes in 20 minutes if they work together.