Is $\sqrt{8+15}$ a rational number or an irrational number?

Simplify $7^{\frac{1}{4}} \cdot 12^{\frac{1}{4}}$.

Find the value of $\sqrt[5]{(243)^{-3}}$.

Express $0.7\overline{39}$ in the form $\frac{p}{q}$,where $p$ and $q$ are integers and $q \neq 0$.

For each question,select the proper option from four options given,to make the statement true: $\sqrt{5} + \sqrt{5}$ is a / an $\ldots \ldots \ldots$ number.

Find five rational numbers between $-\frac{3}{4}$ and $-\frac{1}{3}$.