Because this problem involves simple interest, and the money is only deposited for one year, you can calculate the amount of money in the bank after one year by thinking about a percent increase. Johnny starts with 50 dollars in his bank account, and we are given that he will experience an 8% increase over the year. This means that the amount of money in his bank account after one year is just 50 + 0.08*50 (the principal amount plus the simple interest, or amount of money that increases during the year). This is equal to 50 + 4, or 54 dollars.
Note that, whenever we are dealing with simple interest, the amount of money in the bank after a certain number of years is just P(1 + PRT), where P is the principal amount, R is the interest rate, and T is the number of years the money is in the bank.
