Kinderschokolade (y-3)/5 = (1+y)/2 - (y+2)/4 - 1;
(y-3)/5 = 2(1+y)/4 - (y+2)/4 - 1;
(y-3)/5 = (2+2y-y-2)/4 - 1;
(y-3)/5 = y/4 - 1;
1 = y/4 - (y-3)/5;
1= (5y- 4(y-3)) / 20;
1 = (5y - 4y +12) / 20;
1 = (y+12) / 20;
y+12 = 20;
y = 8.

Проверка совпала.