It's not specified whether 1 is the 1st or 2nd roll: HOWER:
The 1st Roll is "1": P(odd sum/the 1st Roll is 1) What is the sample space of all numbers starting with "1": {(1,1), (1,2), (1,3), (1,4), (1,5), (1,6),} = 6 the couple of add sum=(1,2), (1,4), (1,6), =3 P(odd sum/ 1st is 1) = 3/6 =1/2 or in applying the formula:
P(odd sum/the 1st Roll is 1) =P(odd sum ∩ 1) / P(getting "1") it will give the same probability = 1/2