what is the missing reason in step three?

Triangle inequality theorem state if each set of three numbers can be the lengths of the sides of a triangle. 1. 9, 8, 22. 2. 5,10,12. 3. 7,10,22. 4. 4,11,12. 5. 11,9,10. 6. 10,4,19. 7. 3,12,10. 8. 4,3,2. 9. 6,5,13. 10. 7,12,20. me .

Joe has a rectangular chicken coop. the length of the coop is 4 feet less than twice the width. the area of the chicken coop is 510 square feet. what is the length of the chicken coup?

Plz ( true - false) all triangles have interior angles whose measure sum to 90.