If you take a fixed amount of a solvent, you can add a maximum amount of solute to it. The amount of solute in a solvent is called its concentration. For example, if you add $$20 \, \mathrm{gm}$$ of sugar to $$4 \, \mathrm{liters}$$ of water, the concentration will be $$\frac{20}{4} = 5 \, \mathrm{gm/L}$$
Solution A has a sugar concentration of $$5 \, \mathrm{gm/L}$$. Solution B has a sugar concentration of $$15 \, \mathrm{gm/L}$$. Which is more dilute?