A Solution Contains 100.0 G Of Water, 10.0 G Of NaCl, And 15.0 G Methanol. What Is The Weight Percent Of Methanol In The Solution?

You have 15.0 g of methanol in 125 g of solution.  Percent would be the amount in 100g of solution.  Your proportion looks like this:   15.0g    =    x     x = 12.0% 125.0 g   100.0 g