1. Solve the exponential equation for the variable $x$: $4^{x+2} = 8^x$. The value of $x$ is ___.
2. To solve the equation $49^x = 343$, what is the most efficient common base to use for rewriting both sides of the equation?
3. Find the value of $x$ that satisfies the equation $25^x = \frac{1}{5^{x-9}}$. The value of $x$ is ___.
4. If $16^{x-1} = 64^x$ is rewritten using a common base of 2, which equation correctly represents the relationship between the exponents?
5. Solve for $x$ in the equation $27^{x+1} = 9^{2x}$. The value of $x$ is ___.
6. How many real solutions does the equation $5^x = -25$ have?
7. Solve for $x$ in the equation $3^x = 81$. The value of $x$ is ___.
8. The equation $9^x - 10 \cdot 3^x + 9 = 0$ has two solutions. What is the sum of these solutions? The sum is ___.
9. Which of the following exponential equations can have more than one real solution?
10. How many real solutions does the equation $2 \cdot 10^x + 8 = 4$ have? The number of solutions is ___.