1. **State the problem:** We have a triangle with one exterior angle measuring 70° and an adjacent interior angle of 50°. We need to find the value of the unknown angle $x$ inside the triangle. 2. **Recall the exterior angle theorem:** The exterior angle of a triangle is equal to the sum of the two opposite interior angles. Mathematically, if the exterior angle is $E$ and the two opposite interior angles are $A$ and $B$, then: $$E = A + B$$ 3. **Identify the known angles:** Here, the exterior angle $E = 70^\circ$, one interior angle adjacent to it is $50^\circ$, and the unknown angle is $x$. 4. **Apply the theorem:** Since the exterior angle equals the sum of the two opposite interior angles, and one of those is $50^\circ$, the other must be $x$: $$70 = 50 + x$$ 5. **Solve for $x$:** $$x = 70 - 50$$ $$x = 20$$ 6. **Answer:** The value of $x$ is $20^\circ$.