Don went to his favorite restaurant and ordered a meal. His bill came out to $15.77. He wants to pay a 15% tip. How much did he ended up paying total? pls help!

You want to leave a 15% tip on a meal that cost $15.77.
First, convert the 15% to an actual number that can be used in a calculation. For percents,this is always done by simply dividing the percent (in this case 15%) by 100%.So, the conversational term "15%" becomes 15% / 100% = 0.15 in terms of a real mathematical number.
Second, you need to find out what 15% of your $15.77 meal cost is.This is always done by multiplying 0.15 by $15.77, or

0.15 x $15.77=$2.37.
So, the amount of tip you are going to leave is $2.37.

This makes the total cost of your meal (to write on your charge slip or other payment)

$15.77 + $2.37 = $18.14

$18.14 is your answer

First find out how much interest earned each month by multiplying .07 x 250.00 = 17.50.

Now Mr. Smith deposits 250.00 + 17.50(interest earned) = 267.50 per month

New monthly deposit is 267.50

(New monthly deposit)   267.50 x 39 (months) = 10,432.50

Mr. Smith will have 10,432.50 in the account after 39 months.