The answer is B. replace a 26-year old with a 24-year old because when you get the median of the original ages it’s 26 but if you change it to 24, it will decrease
Let x=gallons of 80% solution to be mixed x+80=gallons go final 70% mixture .. 80%*x+30%*80=70%*(x+80) .8x+24=.7x+56 .1x=32 x=320 gallons of 80% solution to be mixed=320