Question 904215
0.5*x+0.05*9=0.23(9+x)
0.5*x+0.45=2.07+0.23x
0.5x-0.23x=2.07-0.45
0.27x=1.62
x=6 lbs of 50% is added to 9 lbs of 5%  to get  15 lbs  at 23%
check
0.5*6+0.05*9=0.23(9+6)
3+0.45=0.23(15)
3.45=3.45
ok