One canned juice drink is 25% orange juice; another is 5% orange juice. how many liters of each should be mixed together in order to get 20l that is 7% orange juice?

X+y=20
25%x+5%y=7%*20 => 0.25x+0.05y=1.4
miltiply every term in equaition one with 0.25: 0.25x+0.25y=5
subtract equation two from the new equation: 0.20y=3.6 
y=18
x=2
2 liters of the 25% and 18 liters of the 5%

Iam not good at math i wish i could