1 2 21 2 3 36 3 4 43 4 5

1 + 2 = 21 2 + 3 =36 3 + 4 = 43 4 + 5 =?​ And it is not 54

Answers:

4 + 5 = 58  if 1 + 2 = 21 2 + 3 =36 3 + 4 = 43
Step-by-step explanation:

One solution

1 + 2  = 12 + 9  =    21

2  + 3  = 23  + 13 = 36

3 + 4 = 34  + 9  =   43

4 + 5 = 45  +  13  = 58

a + b  = ab  + 9  / 13