Well first you have to convert the fractions so that they can have the same denominator. which would be 16
11/16 stays the same since 1*16 is 16 and 11*1 is 11
5/8 would change to 10/16 since 8*2 is 16 ans 5 *2 is 10 then you add the numerators which is 10 and 11 and it would equal 21/16. the fraction is overweight kr how i call it and then you would simplify which would be 1 5/6
hope this helped:)