Answer:
C 
Step-by-step explanation:
Consider the series

The nth term of series is 
The bottom index tells you that n starts changing from 3, so

Thus, the sum of all terms is

18) (10)7d/10=35(10)
7d/7=350/7
d=50
21) 3/4 w=27
(4/3)3/4 w=27(4/3)
w=36
Hope this helps!
Answer:
It would be 
Step-by-step explanation:
is equivalent to
or
.