39. If 4a = 5b and 5b = 7c, then 4a = 7c
![\Rightarrow Transitive\text{ theorem}](https://img.qammunity.org/2023/formulas/mathematics/college/plg7antuqposrx1p8cy8yf5qk5e2x5z7vn.png)
40. If m∠1 = 25, then m∠1 + 65 = 25 + 65
![\Rightarrow Addition\text{ prop. of}](https://img.qammunity.org/2023/formulas/mathematics/college/n3jetwrpi9am0ktg8btfwwib5mymdhvpe6.png)
41. If m∠1 + m∠2 =90, then ∠1 and ∠1 are complementary.
![\Rightarrow Def\text{ of complementary }\angle^(\prime)s]()
42. If ∠5 and ∠7 are supplementary and ∠7 and ∠2 are supplementary, ∠5 ≅ ∠2
![\Rightarrow Supplements\text{ theorem}](https://img.qammunity.org/2023/formulas/mathematics/college/syz2jcixw4pzorivo5i9musywadn5nula6.png)
43. If ∠1 and ∠3 form a linear pair, then ∠1 and ∠3 are supplementary angles.
![\Rightarrow Linear\text{ Pair Theorem}](https://img.qammunity.org/2023/formulas/mathematics/college/y583cumevi7zedpy974xdbgg6l5q2x53dl.png)