1. The problem asks to identify the unknown angle $x$ and name the congruent pair for each diagram. 2. For part (a), the unknown angle is given as $x = 115^\circ$. 3. The congruent pair is $\angle b$ and $\angle d$. 4. For part (b), the unknown angle is $x = 58^\circ$. 5. The congruent pair is $\angle 58^\circ$ and $\angle x^\circ$. 6. For part (c), the unknown angle is calculated as $$x = 180^\circ - 40^\circ = 140^\circ.$$ 7. The congruent pair is $\angle 1$ and $\angle 2$. 8. For part (d), the unknown angle is calculated as $$x = 52^\circ + 55^\circ = 107^\circ.$$ 9. The congruent pair is $\angle$ head tube angle and the marked bottom-left angle. 10. For part (e), the unknown angle is $x = 50^\circ$. 11. The congruent pair is $\angle c$ and $\angle d$. These answers identify the unknown angles and the congruent pairs as requested.