Question 575599
let investment @ 12% be x
and 6 % be y

x+y = 54000...................1

12%x=6*%y

multiply by 100

12x=6y
x= y/2

substitute x in (1)
y/2 + y =54000

multiply by 2
y+2y= 108000
3y=108000
/3
y=36000

$36,000 @ 6%
$18000 @ 12 %