2. a solution in which 50 grams of salute is dissolved in 250 grams of solution has a concentration of

The fact that the unit is supposed to be in percent makes me think it is referring to percent mass.  To find percent mass you need to find find the divide the mass of solute by the total mass of solution and than multiply that by 100%.
%mass=(50g/300g)x100%
%mass=0.167%

I hope this helps.

All the elements are arranged by melting points on the periodic table. in row they go from metals to gasses. in the row from sodium to argon, sodium is more reactive than the one on its right, magnesium.