11, 18, 25, 32, ..., a8

we notice that we have an A.P where a1= 11 and r= 7

a1= 11

a2= 11+7 = 18

a3= 11+7*2 = 25

a4 = 11+ 7*3= 32

a5= 11 + 7*4= 39

a6 = 11+ 7*5 = 46

a7 = 11+ 7*6 = 53

a8 = 11 + 7*7 = 60

Then the sum is:

S = 11 + 18 + 25 + 32 + 39 + 46 + 53 + 60 = 284

**Then the sum = 284**