Formula:
[tex]a_n=a_1+(n-1)d[/tex]
1.) The common difference is -4-(-7)=3
50th term = -7+(49)3 = -7+147 = 140
2.) 15th term = 1st term + (14)15
40 = 1st term + 190
-150 = 1st term
3) (20-8)d = 20th term - 8th term
12d = 21 - 14
12d = 7
d = 7/12
30th term - 20th term = (30-20)d
30th term - 21 = 10*7/12
30th term = 35/6 + 21
30th term = 161/6 = 26 2/3
4) 16th term = 1st term + 15d = 0.5 + 15(1.5) = 0.5 + 22.5 = 23