If 39 is 100 percent then what is 35
Need answer quick

89.7% is your answer

or 90% if you round it.

This is an Arithmetic Progression with 1st term 11 and common difference d=6

Number of Rows     Number of seats      Common difference " d" 
       
1st                                  a₁     = 11                                 
2nd                                 a₁+d =17               d =2nd - 1st = 6
3rd                                  a₁ +2d = 23           d =3rd - 2nd = 6
4th                                  a₁ +3d = 29            d= 4th - 3rd = 6

nth ROW                         a(n) = a₁ + (n-1)d
18th ROW                       a₁₈ =   11 + (18-1).6 = 11+(17)(6) = 113 

General equation to predict the number of seat an the nth row:
Number of seats in nth row = a₁ + (n-1).d