Kathleen studied 2/3 of the night's in the month. If the month has 30 days, how many nights did she study?

Two thirds of thirty is twenty.

thirty days in a month so split into three is 10 per third

This is a proportion problem.

2/3 = x/30

Cross multiply and divide

30 x2 = 60

60 divided by 3 is 20

Answer is 20

Ps: you could also find the answer by dividing 30 by 3 and that's how you get 1/3 of 3 which is 10. So 2/3 is just 10 + 10 = 20