4 + 4 + 4 + 4 + 3 x 4^2 + 3 x 4^3 + 3 x 4^4 + 3 x 4^5 + 3 x 4^6 =  Choices:
A) 4^24 B) 4^20 C) 4^16 D) 4^12 E) 4^7
Let's see that 4 + 4 + 4 +4 is 4^2, then: 4^2 + 3 x 4^2 becomes 4 x 4^2 that is 4^3. You follow with the next element: 4^3 + 3 x 4^3 is equal to 4 x 4^3 that is 4^4. Then is assumed right before 3 x 4^6: 4^6 + 3 x 4^6 becomes 4 x 4^6 that is 4^7. Thus, the correct answer is the option 4^7, 4^7.
<result>E</result>
4 + 4 + 4 + 4 + 3 x 4^2 + 3 x 4^3 + 3 x 4^4 + 3 x 4^5 + 3 x 4^6 =