Assuming that by Y2 you mean 2 * Y (I'd suggest flipping them for organizational purposes), you'd just plug in for the values. 
So 2(8) + 30 ÷ 6 - 8. PEMDAS says we do the multiplication and division first. 
This gives us 16 + 5 - 8 = 13. 
Again assuming Y2 means 2 * Y in your equation, the answer is 13.