Answer
$0.12x+0.09y.$
Work Step by Step
The combined yearly interest of investing $x$ dollars at $12$ percent and $y$ dollars at $9$ percent is $0.12x+0.09y.$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.