Question 400736
Let add x gallons of water
then will have (x+6) gallons of a 3% insecticide solution 
in a 4% insecticide solution {{{(100-4)=96}}} % of water, so in 6 gallons  of a 4% insecticide solution is {{{0.96*6=5.76}}} gallons of water
in a 3% insecticide solution {{{(100-3)=97}}} % of water, so in (x+6) gallons  of a 3% insecticide solution is {{{0.97(x+6)}}} gallons of water
when will add x gallons of water to 5.76 gallons of water will have {{{0.97(x+6)}}} gallons of water
equation
{{{x+5.76=0.97*(x+6)}}}
{{{x+5.76=0.97*x+5.82}}}
{{{x-0.97*x=5.82-5.76}}}
{{{0.03*x=0.06}}}
{{{x=0.06/0.03}}}
{{{x=2}}} gallons of water