Assuming all the numbers are different, adding the symbols together makes 10, because 4+3+2+1+0=10, so "8"=1 and "B"=0. But if B=0, y=yy and a, y and £ match one of the following 6 sets: 234, 243, 324, 342, 423 or 432 (ay£). We know a£-y8 is positive so a is bigger than y, so we have the sets 324, 423 or 432. These make the following sums: 34-21=13; 43-21=22; 42-31=11. so for consistency, y must be 2, and a=4 and £=3.
Substituting in all the equations we have: 4+0+2+1+3=10; 43-21=22; 2+0=2 (matching the title question), and so y+B=y, not yy.