ANSWER:
$5000 was invested at 4% and $2500 was invested at 12%.
STEP-BY-STEP EXPLANATION:
We have that she has 7500 and invests an unknown amount, we will call x at 4%, then she has 7500-x to invest at 12%.
Therefore, we can plan the following equation:
[tex]0.04\cdot x+0.12\cdot\mleft(7500-x\mright)=500[/tex]Solving for x:
[tex]\begin{gathered} 0.04x+900-0.12x=500 \\ -0.08x=500-900 \\ x=\frac{-400}{-0.08} \\ x=5000 \end{gathered}[/tex]Therefore she, 5000 $ at 4%, to calculate at 12% it would be:
[tex]7500-5000=2500[/tex]It means that at 12% she invested $ 2500
