Question 903227
1*x+0.3*20=0.5(20+x)
1*x+6=10+0.5x
1x-0.5x=10-6
0.5x=4
x=8 gallons of 100% is added to 20 gallons of 30% to get  28 gallons  at 50%
check
1*8+0.3*20=0.5(20+8)
8+6=0.5(28)
14=14
ok