R - элемент
X - вещество
Mr (MgCa(CO₃)₂) = 24 + 40 + 2*12 + 6*16 = 184
w (Mg) = 24/184 = 0,13 = 13%
w (Ca) = 40/184 = 0,217 = 21,7%
w (C) = 2*12/184 = 0,13 = 13%
w (O) = 6*16/184 = 0,522 = 52,2%
Mr (NH₄NO₃) = 2*14 + 4*1 + 3*16 = 80
w (N) = 2*14/80 = 0,35 = 35%
w (H) = 4*1/80 = 0,05 = 5%
w (O) = 3*16/80 = 0.6 = 60%