Question 930689
Let first term be a1

d=1

Sn = n/2(a+l)  .... l is the last term a is the first term

S9 = 9/2(1+9) =45

S10 = 10/2(1+10) =55

S11= 11/2 (1+11) = 66

Add them up 45+55+66 thats your answer