To start we need to set up an equation to find the initial investment at 7.5%.
[tex]\begin{gathered} .075I+.065(I-4000)=1000 \\ .075I+.065I-260=1000 \\ .14I=1260 \\ I=9000 \end{gathered}[/tex]So the amount invested at 7.5% is 9000 and the amount invested at 6.5% is 9000-4000 which equals 5000.