Mr(MgSiO3) = Ar(Mg) + Ar(Si) + 3 × Ar(O) = 24 + 28 + 3 × 16 = 24 + 28 + 48 = 100
ω(Mg) = (Ar(Mg) / Mr(MgSiO3)) × 100% = (24 / 100) × 100% = 24%
ω(Si) = (Ar(Si) / Mr(MgSiO3)) × 100% = (28 / 100) × 100% = 28%
ω(O) = (3 × Ar(O) / Mr(MgSiO3)) × 100% = (3 × 16 / 100) × 100% = (48 / 100) × 100% = 48%
Ответ: ω(Mg) = 24%, ω(Si) = 28%, ω(O) = 48%