You made two deposits to your bank account this month. one deposit was $24.61, and the second deposit was $16.49. your balance at the end of the month is $72.31, and you made no withdrawals. write and evaluate an expression for your balance at the beginning of the month.

First you have to find out how much money you have put in this month, so you need to add your two deposits together. 

24.61 + 16.49 = $41.10

Now we know that this month you put $41.10 in your account, but there is a total of $72.31 in your account. Now you need to subtract what you put in this month to your total amount.

72.31 - 41.10 = $31.21 was your balance at the beginning of the month.