51 g sodium nitrate is dissolved in water to make 787 g of solution. What is the percent sodium nitrate in the solution?

Answer in units of%.

I assume you want %w/w.

%w/w = g solute/100 g solution or (g solute/g solution)*100 = ?
So we can say 51 g NaNO3 per 787 g solution; convert to 100 g solution this way; i.e., 51 x (100/787) = ?
or (g solute/g solution)*100 = (51/787)*100 = ?