Dilution by C₁V₁ = C₂V₂, and the mass to weigh out for a solution of a given concentration.
The two sums people reach for a calculator to do with solutions.
Dilution. Leave one of the four fields empty and it is worked out. It will also tell you how much solvent to add.
From a weighed solid. Enter the formula, the concentration you want and the volume, and get the mass to weigh. The molar mass comes from the formula, so there is nothing to look up.
Everything happens in your browser; nothing is sent anywhere. The atomic masses are the ones on the element pages.
A formula can be checked in the molar mass calculator, which shows the breakdown by element.