Answer:
[tex]s = 19z - 7 - (5z - 9) - (8z + 3) \\ = 19z - 7 - 5z + 9 - 8z - 3 \\ = (19z - 5z - 8z) + (9 - 7 - 3) \\ \therefore \: third \: side \: s= 6z - 1[/tex]
