like in the same way 5+7=13 it is given as 5+7=12 and add one to it then it is 12+1=13

but when u compared with first option and third option the answer can be given as

5+7=85

because replace 7 with 17 then multiply with 5 ie 17*5=85

because 2+7=34

how in the sense replace 7 with 17 multiply with 2 therefore 2*17=34

like same way third option

6*13=78 i.e replace 3 with 13 and multiply with 6

so the final answers are 13 and 85

2 + 7 means 2 * (10+7) = 34

6 + 3 6 * (10+3) = 78

then 5 + 7 could mean 5 * (10+7) = 85

But 8 + 9 is not fitting in this pattern.