Answer:
[tex]0.03x+2700[/tex]
Step-by-step explanation:
We are asked to find the combined yearly interest for both amounts.
The interest for x dollars invested at 12% would be 12% of x.
[tex]12\%\text{ of }x=\frac{12}{100}\cdot x=0.12x[/tex]
The interest for [tex]30,000-x[/tex] dollars at 9% would be 9% of [tex]30,000-x[/tex].
[tex]\frac{9}{100}(30,000-x)[/tex]
[tex]0.09(30,000-x)[/tex]
[tex]2700-0.09x[/tex]
Combined interest:
[tex]2700-0.09x+0.12x[/tex]
[tex]2700+0.03x[/tex]
[tex]0.03x+2700[/tex]
Therefore, the combined tax would be [tex]0.03x+2700[/tex].
