So 18 times ten gives us 180. The moles cancel, we're left with grams. So 180 grams of water in our beaker. Now we know we want to create a 5% bimass solution of sodium chloride, so we use the formula 5% is equal to the number of sodium chloride we need to add in terms of grams divided by the total number of grams. So 180 grams of water that we already have, plus the x. The x is the number of sodium chloride in grams that we need to add multiply the whole thing by 100.