How many 4-digit numbers can be formed using only the digits 9, 8 and 7?

How many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.) how many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.)

In the next 10 month,colin wants to save $900 for his vacation.he plans to save $75 each of the first 8 months. how much must he save each of the last 2 months in order to meet his goal if he saves the same amount each month ?

Allen wants to buy a hover board that sells for $249.99 and a helmet that is $36.54. how much change will allen receive if he gives the cashier three $100.00 bills?