1. **Stating the problem:** We have a triangle with an exterior angle measuring 141° and an adjacent interior angle labeled $x^\circ$. The triangle has a right angle at the top vertex. 2. **Formula used:** The exterior angle of a triangle is equal to the sum of the two opposite interior angles. In symbols, if $\theta_{ext}$ is the exterior angle and $\alpha$, $\beta$ are the two opposite interior angles, then: $$\theta_{ext} = \alpha + \beta$$ 3. **Applying the formula:** Here, the exterior angle is 141°, one interior angle is the right angle (90°), and the other interior angle is $x^\circ$. So: $$141 = 90 + x$$ 4. **Solving for $x$:** $$x = 141 - 90$$ 5. **Calculating:** $$x = 51$$ 6. **Answer:** The value of $x$ is $51^\circ$. This means the interior angle adjacent to the exterior angle of 141° is 51°.