chemistry
posted by What? .
How do I determine the mass (in g) of a sucrose solution that contains 12g of sucrose and is 4.1% sucrose by mass?

4.1% w/w sucrose means 4.1 g sucrose per 100 g solution. [The 100 g solution will be made up of 4.1g sucrose + 95.9 g H2O but that isn't needed to weork the problem.]
100 g soln x (12g/4.1g) = ? g soln.
There is another way to do it; some students prefer this method. Just plug into the % equation.
% = (mass solute/g solution)*100 = ?
4.1 = (12/x) and solve for x.