I need help with this, I have watched the "help videos" but nothing seems to click. the answer wants me to find liters. I don't understand how to turn this into liters. When I watch the help videos it seems like the guy is pulling numbers fro then air. please help.

Ashley mixes two types of soft drinks. One soft drink has 20% sugar; the other drink has 45% sugar. Ashley wants to produce one liter of a mixture containing 40% sugar.

Set up and solve an equation using the weighted average of concentrations to decide how much of the 20% sugar Ashley should use.