Question

What do I do ? I’m stuck on these question because I don’t remember this from previous lessons.

Answer 1

Answer: 21 (choice C)

Reason:

The fancy looking "E" is the Greek uppercase letter sigma. It represents "summation". We'll be adding terms of the form
`3(2)^k` where k is an integer ranging from k = 0 to k = 2.

• If k = 0, then
  `3(2)^k = 3(2)^0 = 3`
• If k = 1, then
  `3(2)^k = 3(2)^1 = 6`
• If k = 2, then
  `3(2)^k = 3(2)^2 = 12`

Add up those results: 3+6+12 = 21

Therefore,
`\displaystyle \sum_(k=0)^(2) 3(2)^k = \boldsymbol{21}`

which points us to choice C as the final answer.