Question

no. of moles of ammonia that have same mass as that of 3 moles of carbon-dioxide has

Answer 1

1 mole of CO2 = 44 g
Mass of 3 moles of CO2 = 3 ×44 = 132 g
Molar mass of NH3 = 17 g
Hence , number of moles = Given mass / molar mass
Number of moles = 132 / 17 = 7.7 moles

Answer 2

 Well, we know that molar mass of CO2 is 44 grams
so one mole of carbon dioxide contain 44 grams
So 3 moles of carbon dioxide will contain =44*3 =132 grams
Similarly one mole of ammonia contain 17 grams 
we also know that number of moles = mass of given substance/molar mass 

So number moles of NH3 having mass as that of 3 mole of Carbondioxide = 132/17 =7.7 moles of ammonia which is our answer