Question

Calculation in grams for a .100 M solution of NaC2H3O2 * 3H2O using a 100 mL volumetric flask?

Answer 1

How many mols do you want? That is M x L = ?

Then mols NaC2H3O2 = grams NaC2H3O2/molar mass NaC2H3O2.
Solve for grams.