Question

Dunno what i'm exactly supposed to be doing here?

Answer 1

You have to add the first year then for the 2nd year you have to add the estimated difference

Answer 2

The total change means add the changes from each year
-1 3/5 + (- 2 1/15) = 
-8/5 - 31/15 =
-24/15 - 31/15 =
-55/15 = - 3 2/3<== the total change