algebra(check)

I'm pretty sure these are right but I just want to check.

1)Find the 20th term of the arithmetic sequence in which a1=3 and d=7
a.143
b.136
c.140
d.133

2)Write an equation for the nth term of the arithmetic sequence -3,3,9,15...
a.an=n+6
b.an=6n+9
c.an=6n-9
d.an=n-3

3)Find the two arithmetic means between 4 and 22
a.10,16
b.8,16
c.8,12
d.13,13

4)Simplify:Find Snfor the arithmetic series in which a1=3,d=1/2,and an=15
a.225
b.9
c.45
d.210

5)I don't know how to type this but its like this in my book.
Find; 8 is on top of the sigma notation and k=3 is at the bottom(40-3k) is on the right side
a.45
b.282
c.-90
d.141

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2. 👎 0
3. 👁 144

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