How many liters of a 70% acid solution must be mixed with a 25% acid solution to get 360 L of a 60% acid solution?

x+y=360.

0.7x+0.25y=0.6*360.

0.7x+0.25(360-x)=216.

0.7x+90-0.25x=216.

0.45x=216-90.

0.45x=126.

x=126/0.45

=280.

y=360-280=80 liters.

70% acid solution in liters=280.

25% acis solution in liters =80.