[tex]\frac{4+21}{2}[/tex]
1) Let's turn that from English to Math:
[tex]\frac{8+\sqrt{84}}{4}[/tex]
2) Note that we can rewrite that and then factor out the GCD to rewrite it as a product and simplify it as much as we can.
[tex]\begin{gathered} \frac{8+\sqrt{84}}{4} \\ \frac{8+\sqrt{2^2\cdot\:3\cdot\:7}}{4} \\ \frac{8+2\sqrt{21}}{4} \\ \frac{2\left(4+\sqrt{21}\right)}{4} \\ \frac{2\left(4+\sqrt{21}\right)}{2\cdot \:2} \\ \frac{4+\sqrt{21}}{2} \end{gathered}[/tex]
Note that in the options the terms are flipped, but this is not a problem. So we can tell that the answer is:
