A solution containing 30% insecticide is to be mixed with a solution containing 50% insecticide to make 200 L of a solutions containing 42% insecticide. How much of each solution should be used?

Let x L of solution 1 is used

and 2nd solution is (200-x) L

According to question,

30% of x + 50% of (200-x) = 42% of 200L

0.3x + 0.5 (200-x) = 84

0.3x - 0.5x + 100 = 84

0.2x = 16

x=80

Therfore 80L of solution 1 and 120L of solution 2 is mixed.