Question 102326
10 gallons of 20% antifreeze have {{{10 x 20/100}}} or {{{2}}} gallons of antifreeze, that's 20% antifreeze, 80% water. 
So you currently have 2 gallons of antifreeze and 8 gallons of water. 
For a 50% solution, you need 50% water and 50% antifreeze. 
You have 8 gallons of water so you need 8 gallons of antifreeze for a 50% solution. 
You have 2 gallons of antifreeze. 
You need 8 gallons of antifreeze. 
You need to add{{{8-2 }}} gallons of antifreeze. 
Your answer is 6 gallons.