C8H8---- больше X---- больше C6H6---- больше Y----- больше C8H8    

1) 3C6H5-CH=CH2 + 5K2Cr2O7 + 20H2SO4 = 3C6H5-COOH + 3CO2 + 5K2SO4 + 5Cr2(SO4)3 + 23H2O;   2) C6H5-COOH + NaOH = C6H5-COONa (X) + H2O;   3) C6H5-COONa + NaOH (+T) = C6H6 + Na2CO3;   4) C6H6 + C2H4 (+T, AlCl3) = C6H5-CH2-CH3 (Y);     5) C6H5-CH2-CH3 (+T, Fe2O3/Cr2O3 + K2CO3) = C6H5-CH=CH2 + H2.