Question 1053320
0.55x+0.8(50-x) = 0.6(50)
0.55x+40-0.8x = 30
-0.25x = -10 divide both sides by -0.25 and remember -/- = + 
x = 40 
You need 40 gallon of the 55% acid solution and 50-40 = 10 gallon of the 80% solution to get 50 gallon at 60%