Question

what is the ratio by mass calcium chloride

Answer 1

Calcium Chloride is CaCl2 

You need to get the MW (molecular weight) 
Ca = 1 x 40.08 = 40.08 
Cl = 2 x 35.453 = 70.906 
= 110.986 g/mol 

Ca = (40.08 / 110.986) x 100 = 36 % 
Cl = (70.906 / 110.986) x 100 = 64% 

64% is the percent by mass of Cl

Answer 2

40g Ca combine with 71g Cl give-

$111g \: CaCl_{2}$

Plz refer to the pic given

Hope It Helps