There are 45 new houses being built in a neighborhood. Last month, 1/3 of them were sold. This month, 1/5 of the remaining houses were sold. How many houses are left be sold?

45 new houses ... last month 1/3 were sold ...

1/3 (45) = 45/3 = 15 houses sold last month

this month, 1/5 of the remaining houses were sold ...

remaining houses left are (45 - 15) = 30

1/5 (30) = 30/5 = 6 houses sold this month

houses left : 45 - 15 - 6 = 45 - 21 = 24 houses remain <==