When a solid mixture of mgco3 and caco3 is heated strongly, carbon dioxide gas is given off and a solid mixture of mgo and cao is obtained. if a 24.00 g sample of a mixture of mgco3 and caco3 produces 12.00 g co2, then what is the percentage by mass of mgco3 in the original mixture? express your answer u?

MgCO3---> MgO +CO2  , x mol MgCO3       
M(MgCO3)=24.3+12.0+48.0=84.3 g/mol

CaCO3--->CaO+CO2   , y mol CaCO3   
M(CaCO3)=40.0+12.0+48.0=100g/mol     
M(CO2)=44.0

x*84.3 + y*100=24.00
x*44+y*44=12.00            x+y=12/44=0.2727, x=0.2727-y
(0.2727-y)*84.3 + y*100=24.00
22.99-84.3y+100y=24.00
22.99+15.7y= 24.00,     15.7y=1.01,    y=0.06430 mol CaCO3
x=0.2727-0.06430=0.2084 mol MgCO3
0.06430 mol CaCO3*100g/mol=6.43 g CaCO3
0.2084 mol MgCO3*84.3g/mol=17.57 g MgCO3
what does it mean express your answer u?