Calculate the percent concentration of a 9.28N NaOH solution of density 1.31g/ml?

9.28 moles/L x 40.0 g/mole = 371.2 g/L 
1 L x1.31 g/mL x 1000 mL/L = 1310 g 
371.2 / 1310 g = 0.283 
28.3 % by weight