\(a.\)
\(m_{hh}=m_{SO_2}+m_{CO_2}=0.15\cdot64+0.2\cdot44=18.4\left(g\right)\)
\(n_{hh}=0.15+0.2=0.35\left(mol\right)\)
\(\overline{M}_X=\dfrac{m_{hh}}{n_{hh}}=\dfrac{18.4}{0.35}=52.5\left(\dfrac{g}{mol}\right)\)
\(b.\)
\(d_{X\text{/}NO_2}=\dfrac{52.57}{46}=1.14\)