The logic follows here is: In Rows, (1st term + 3rd term)/2 = 2nd term → Row 1=(9,15,21) - (9+21)∕2=30∕2=15 → Row 2=(8,17,26) - (8+26)∕2=34∕2=17 → Row 3=(?,43,35) - (?+35)∕2=43 ?=86−35 ?=51 Thus, the missing term is ' 51 '. Hence, the correct answer is "51".