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

18 - half of 12 =12 so 12 is the answer

Comments

if 2 × 8 = (_) × (_) then (_) = (_)

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how about 15?
2+6-3=5
4+9-6=7
6+11-9=8
8+15-12=11
12+18-15=15

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This ans is wrong

Answer 2

Answer = 12
a,b = b - a/2
2,6=5 -> 6 - 2/2 = 5
4,9=7 -> 9 - 4/2 = 7
6,11=8 -> 11 - 6/2 = 8
8,15=11 -> 15 - 8/2 = 11
then
12,18= -> 18 - 12/2 = 12

Comments

Looks correct but 15 is also right

6+2-(3*1) 5
4+9-(3*2) 7
6+11-(3*3) 8
.
.
.

Answer 3

2+6-3=5
4+9-6=7
6+11-9=8
8+15-12=11
12+18-15=15
The answer is 15.

Answer 4

Ans:11

2,6=5----> 5+2=7-1=6(ans+1st num)-(2nd num)
4,9=7----> 7+4=11-2=9
6,11=8-> 8+6=14-3=11
8,15=11-->11+8=19-4=15

12,18=11--->11+12=23-5=18