Find the 7th partial sum of (infinit) over e and under e is i=1, then the equation on the right side of e is 6(3)^(i-1).
*the e is the sigma notation symbol*

The partial sum can be determined through the calculator or substituting the value to the variable manually. 

6(3)^(1-1) = 6
6(3)^(2-1) = 18
6(3)^(3-1) = 54  
6(3)^(4-1) = 162 
6(3)^(5-1) = 486
6(3)^(6-1) = 1458
6(3)^(7-1) = 4374

total is   6558