Tell whether each sequence is arithmetic. If the sequence is arithmetic,
identify the common difference and find the indicated term.
18. -9, -4, 1, 6, 11, ...;a7=?
19. 2, 4, 7, 11, 16, 22, ...; a9= ?
20. -7,-1, 5, 11, 17,...; a6 = ?
21. 1.2, 1.9, 2.6, 3.3, 4.0, ...; a8 = ?
22. 3, 5/2,3/2,-3/2,....;a7=?
PLEASE HURRRY THIS REALLY URGENT‼️ SOMEBODY HELP