Question 905414
0.02*x+0.08*15=0.05(15+x)
0.02*x+1.2=0.75+0.05x
0.02x-0.05x=0.75-1.2
-0.03x=-0.45
x=15 gal of 2% is added to 15 gal of 8%  to get  30 gal  at 5%
check
0.02*15+0.08*15=0.05(15+15)
0.3+1.2=0.05(30)
1.5=1.5
ok
Note that 5 is the average of 2 and 8 so we need equal amount of 2% and 8%