James callahan has available a 10% alcohol solution and a 60% alcohol solution. find how many liters of each solution he should mix to make 50 liters of a 40% alcohol solution?

Let
x> liters of 10% alcohol solution
y> liters of 60% alcohol solution

we know that
x+y=50> x=50-y> equation 1
0.10x+0.60y=0.40*50> 0.10x+0.60y=20> equation 2

substitute 1 in 2 
0.10*(50-y)+0.60y=20> 5-0.10y+0.60y=20
5+0.50y=20> 0.50y=15> y=30
x+y=50> x=50-30> x=20

the answer is
20 liters of 10% alcohol solution
30 liters of 60% alcohol solution

The decimal expansion would be .27 repeated