Question

Y2 + 30 ÷ x - 8 what is the value of the expression when x = 6 and y = 8?

Answer 1

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. 

Answer 2

Y2 + 30 ÷ x - 8  i think this y power 2 ??

8 power 2   + 30 ÷  6  -  8  =

64  + 30 ÷  6  -  8  = 

64 +5-  8 =  61 

we use first the power then the multiplication or division and the last addition and subtraction