Helpi do not know i dont get i

The amount invested at 4% is $20,500 and the amount invested at 10% is $500

Step-by-step explanation:

Let

x -----> the amount invested at 4%

(21,000 -x) ----> the amount invested at 10%

we know that

The interest of the amount invested at 4% plus the interest of the amount invested at 10% must be equal to $870

so

Solve for x

therefore

The amount invested at 4% is $20,500 and the amount invested at 10% is $500