Simple interest does not allow for interest-on-interest and is only based on the principal amount (original amount). The formula for simple interest is I=P⋅r⋅t, with I being interest, P being the principal, r being the interest rate, and t being the amount of times interest has added. By plugging in everything you know, you get
I = 600⋅0.01⋅2
The rate is 0.01 because 1% converted into a decimal is 0.01. After multiplying all the numbers, you'll find that the total amount of interest he gains is $12. Add that to his principal of $600 and you'll see that Mike now has $612 in his savings account after two weeks.
