Answer:
[tex]\begin{equation*} 2a+8\text{ }\sqrt{b} \end{equation*}[/tex]Step-by-step explanation:
Simplifying,
[tex]\begin{gathered} \sqrt{9a^2}+\sqrt{49b}-a+\sqrt{b} \\ \rightarrow3a+7\text{ }\sqrt{b}-a+\sqrt{b} \\ \rightarrow2a+8\text{ }\sqrt{b} \end{gathered}[/tex]