Question

Paulina invested $10,000 at two different rates, 4% and 6%. If her total interest income was $470, how much did she invest at each rate.

Answer 1

0.04x+0.06(10000-x)=470
Solve for x
X=6500 at 4%
10000-6500=3500 at 6%

Answer 2

a+b=10000 (1)

4%a+6%b = 470
4a+6b = 47000 (2)

(1)*6 =>
6a+6b = 60000 (3)

(3)-(2)=>
2a=13000 =>

a = 6500
b = 3500