Answer:
B
Step-by-step explanation:
20x - 5 - 2x = 31
18x = 36
x = 2
The answer is 9.
Explanation: 21÷ 2 1/3= 9
∑ (n = 1 to 5) (2·(-4)^(n - 1))
S5 = 2·((-4)^5 - 1)/((-4) - 1) = 410