7.198. $\left(3 \cdot\left(3^{\sqrt{x}+3}\right)^{\frac{1}{2 \sqrt{x}}}\right)^{\frac{2}{\sqrt{x}-1}}=\frac{3}{\sqrt[10]{3}}$.
## Solution.

Domain of definition: $0<x \neq 1$.

From the condition

$$
3^{\frac{3(\sqrt{x}+1)}{2 \sqrt{x}} \cdot \frac{2}{\sqrt{x}-1}}=3^{\frac{9}{10}} \Leftrightarrow \frac{3(\sqrt{x}+1)}{2 \sqrt{x}} \cdot \frac{2}{\sqrt{x}-1}=\frac{9}{10} \Leftrightarrow 3 x-13 \sqrt{x}-10=0
$$

Solving this equation as a quadratic equation in terms of $\sqrt{x}$, we get $(\sqrt{x})_{1}=-\frac{2}{3}$ (not suitable), or $(\sqrt{x})_{2}=5$. Therefore, $x=25$.

Answer: 25.