John wants to make 15 L of a 71% alcohol solution by mixing together a 80% alcohol
solution and a 65% alcohol solution. How
much of each solution must he use?

Step-by-step explanation:

To answer this question we must understand what does each percentge mean :

For 71 percent alcohol we have the quantity wich is 15 liter

so :

15 liter⇒ 100 percent

x( the unkhown quantity)⇒ 71 percent

x = (15*71)/100 )= 10.65 liter of alcohol

so we want 10.65 liter of alcohol

here is a way :

lat's take 10 L of 80 percent alcohol and 4liters of  the other one

10*0.8+4*0.65 = 10.6

we just need 0.05 liter of alcohol

add 0.0625 L of the 80 percent liter alcohol to get 10.65

idk