= 80.5 - (80 + 0.5) + 28 + 5/6
= 80.5 - 80.5 + 28 + 5/6
= 28 + 5/6
= 28 + 0.8333
= 28.8333

Therefore, 80.5 - (у-80 5/10) + 28 5/6 is equal to 28.8333.