How much was invested at each rate?

Question

$5900 is invested, part of it at 12% and part of it at 7%. For a certain year, the total yield is $568. How much is invested at each rate?

Answer 1

.12(x) + .07(5900-x) = 568

.12x -.07x =568 - 5900(,07) = 568-413 = 155

.05x = 155

x = 155/.05 = $3,100 invested at 12%

(5900-x) = $2,800 invested at 7%

.12(3100) + .07(2800) = 568

372 + 196 = 568