To solve this problem you might have to use this formula y=a(1+r)^t A=amount of money you already have 1= a set number R= rate T= time YOUR GIVENS ARE: A=4000 R= 3.5% (0.035) decimals T= 3 years NOW lets plug IN everything in the FORMULA y=4000(1+.035)^3= $4434.87. NOW lets subtract 4000-4434=434. She earned $434 of simple interest.