Question 1170828
Let x = the number of liters of orange punch in the fruit punch. 
Then the number of liters of mango is 500 - x
The number of liters of orange + mango juice is 
0.45x + 0.2(500 - x), and this must equal the number of liters 
in the fruit punch, which is 0.4*500
0.45x + 100 - 0.2x = 200
0.25x = 100 -> x = 400 L