Asample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium. how much calcium is contained in 45.0 g of calcium fluoride

              23.1 g of Ca

It is a simple proportional problem in which we will find either the increased or decreased value of calcium with proportional to Calcium fluoride.

Therefore as given,

                      15.0 g of pure CaF₂ contains  =  7.70 g of Ca

So,

                45.0 g of pure CaF₂ will contain  =  X g of Ca

Solving for X,

                       X =  (45.0 g × 7.70 g) ÷ 15.0 g

                       X  =  23.1 g of Ca

Hence, as the amount of CaF₂ has increased from 15.0 g to 45.0 g therefore, the amount of Ca it contained also increased from 7.70 g to 23.1 g.

that's what i got you can count the number of atoms