Question

you invested 12000 in two accounts paying 5% and 7% annual interest. If the totak interest earned for the year was 760 how much was invested at each rate?

Answer 1

12000*0.05=600
12000*0.07=840
Proportion at 5% = (840-760)/(840-600)=1/3
Proportion at 7% = (760-600)/(840-600)= 2/3 (or 1-1/3=2/3)
(1/3) of 12000 = 4000 at 5%
(2/3) of 12000 = 8000 at 7%

Answer 2

or
amount invested at 5% --- x
amount invested at 7% --- 1200-x

.05x + .07(12000-x) = 760
5x + 7(12000-x) = 76000
-2x = -8000
x = 4000 at 5% , then 12000-4000 or 8000 at 7%