The formula for simple interest is I=prt. Where I is the interest, p is the principle (investment), r is the rate, and t is the time. Plugging in the numbers you know, you get I=(3000)(0.05)(20). Simplifying, you get I=3000. This is the interest that you get. To get the total money you have, add that to the original amount(investment) to get $6000.
Interest: $3000
Total: $6000
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