How many molecules are in 165 g of carbon dioxide?

Here is the order of steps you take to figure out this question:
First you need to know how many moles you would get from 165 g of carbon dioxide. You do that by doing: 
Carbon = 12
Oxygen 2 = 16 x 2 = 32
Total: 32 + 12 = 44  

 -Next you have to use proportions
1 mol CO2 x 1 mol CO2 44 g
= or =
44 g 165 x 165 g

165/44 = 3.75 moles CO2  

 - Last step is to multiply the amount of moles by Avogadro's number, 6.02 x 10^23
3.75 x 6.02 x 10^23 = 2.25 x 10^24 molecules 

Hope this helped