Answer:
See explanation
Explanation:
1. Parallel lines t and g are cut by transversal c. Angles 1 and 9 are corresponding angles when two parallel lines t and g are cut by transversal c. By corresponding angles theorem, corresponding angles are congruent, so
![\angle 1\cong \angle 9](https://img.qammunity.org/2021/formulas/mathematics/middle-school/rfyzlxmdzbii8zec4foq3y7j1dpdbcz7x4.png)
2. Parallel lines c and d are cut by transversal g. Angles 9 and 14 are same-side exterior angles when two parallel lines c and d are cut by transversal g. By same-side exterior angles theorem, same-side exterior angles are supplementary (add up to 180°), so
![\angle 9+\angle 14=180^(\circ)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/46zecelkhn7ejrohsw4hgkanavbq3wd9wp.png)
3. By substitution property,
![\angle 1+\angle 14=180^(\circ)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/5ndlercqtoxwr5nf1e15s2958t9u6upddy.png)