[tex]\begin{gathered} \text{The missing number is 21,} \\ \text{because it is the }multiple\text{ of 7.} \\ \Rightarrow7,14,21,28,35 \\ \text{Now, the ratio,} \\ \Rightarrow\frac{7}{2}=3.5 \\ \Rightarrow\frac{14}{4}=3.5 \\ \Rightarrow\frac{21}{6}=3.5 \\ \Rightarrow\frac{28}{8}=3.5 \\ \Rightarrow\frac{35}{10}=3.5 \\ So,\text{ the answer is }\Rightarrow3.5 \end{gathered}[/tex]
