If 2,6=5 4,9=7 6,11=8 and 8,15=11 then 12,18=?

Question

If
2,6=5
4,9=7
6,11=8
8,15=11
then
12,18=?

Answer 1

12

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6-2/2=5
9-4/2=7
11-6/2=8
15-8/2=11
18-12/2=12

Answer 2

2 6 5 5
4 9 7 7
6 11 8 8
8 15 11 11
12 18 12

Answer 12

Answer 3

12, cause answer should be half of first number subtracted from second number.

Answer 4

2, 6 = 5 (Two Six = 6 letters - 1 = 5; simlarly
4, 9 = 7 (Four Nine =) 8 letters - 1 = 7 and so on.
The formula is -
The total number. of letters in the given set of numbers - 1 = the answer;
Therefore, 12, 18 = Twelve (6) + Eighteen (8) = 14 letters - 1 = 13.

The answer: 12, 18 = 13