[Math] If there is a 30% chance of rain for both Saturday and Sunday, what is the probability there would be rain on both days

probability

Can someone give me a formula for this question?

Wanda said there was a 30% chance of rain for both Saturday and Sunday. It rained on both days.

If her calculations were correct and there was a 30% chance of rain each day, what is the probability there would be rain on both days?

Please help!!!