For anyone who didn't get it, this is not a math equation but a sequence logic. 3, 4, 5 and 6 follow a logic... 3-1 = 4 is the starting point of a sequence that directly indicates that the question is not looking for the answer of a mathematical equation. Instead the question wants you to identify the logic behind the "statement" 3-1=4 and apply the same logic to the following incomplete sequences. By replacing "-" with a "+" and replacing the redundant value of 1 with another sequence of numbers following 1 (as the starting statement already started with 1) You just follow the sequence for the succeeding "statements" Ergo, 4-1=6, because it became 4+2=6 5-1=8, because it became 5+3=8 So... 6-1=10 because then it would have been 6+4=10, following the sequence logic on the previous examples/statements..