Answer:
105mg of calcium chloride

Step-by-step explanation:
The molecular formula of calcium chloride is
and the molecular formula of soda ash is

First of all you should write the balanced reaction between both compounds, so:

Then you should have the molar mass of the two compounds:
Molar mass of

Molar mass of

Now with stoichiometry you can find the mass of calcium chloride that reacts with 100mg of soda ash, so:
