\(n_{CO_2}=a\left(mol\right),n_{N_2O}=b\left(mol\right),n_{H_2}=c\left(Mol\right)\)
\(n_A=a+b+c=0.05\left(mol\right)\)
\(\Leftrightarrow44a+44b+44c=2.2\left(1\right)\)
\(m_A=44a+44b+2c=1.78\left(g\right)\left(2\right)\)
\(\Rightarrow c=0.01\)
\(m_B=0.01\cdot2+0.03\cdot X=0.14\left(g\right)\)
\(\Rightarrow X=4\)
\(X:He\)