To add any fraction You need to make sure that the denominator of the fractions are same. ( denominator in your sum is 19 )
10/19 + 3/19 ( we have the same denominator )
we can also write this problem like
( 10 + 3 ) / 19 { add the numerators together }
13 / 19
So correct option is B.
hope this helped.. :)